Orchid

There are literally tens of thousands of species, cultivars and varieties in the orchid family, the largest family of flowering plants. The word orchid may refer to any of the botanical family Orchidaceae, or, more commonly among lay persons, any of thousands of flowers called "orchids".

Orchids have been cultivated for centuries. They range from rare and recent discoveries such as the tiny Tallong Midge Orchid to the large, showy orchids which are featured in bouquets and corsages, to food orchids such as Vanilla. A few orchids have insignificant flowers and are grown for their foliage. Because orchids are generally epiphyte plants, the material available for their nourishment is scarse and the water is available only from the rain and humidity from the air, therefore orchids learnt how to maximize the utilization of the few available resources. They adapted to keep water in their thickened, almost succulent stems, called pseudobulbs, or in highly porous roots recovered by a spongy layer called vellamen, capable of absorbing humidity from the air; or in thick leaves; and yet, when terrestrial, in small root tubers. For the same reason, they are plants that go through long periods of rest when their metabolism is reduced, followed by a fast growth, blooming during the time of the year when the resources are more abundant or immediately thereafter. Many species loose their leaves to avoid dehydration during the droughs or while they are resting.

Orchids seemed to be fascinating: every developed nation has many orchid societies, and this fascination extends beyond form and beauty. Because of their biological importance (some orchids have developed extraordinary systems of pollination, for example, "Lady's Slipper" traps insects and so forces them to pollinate the flower; one Australian orchid exists underground and is pollinated by ants; many give off attractive odours), orchids hold just as much interest for scientists. Famed biologist Ernst Mayr discovered and named 38 new species of orchid.

Distribution
Orchids can be found in almost all regions of the planet, except Antarctica. Due to their wide geographic distribution, it is natural that a so diverse group of plants show high degree of adaptation to different climates and to the multiplicity of pollinators present in each area. The number of orchid genera that exist on every continent is not exact because there is no consensus among the taxonomists about how to split them, however, it can be estimated as follow: Eurasia, about 50 genera; North America, circa 25 genera, Latin America and Caribbean, between 300 and 350; tropical Asia, between 250 and 300; tropical Africa, circa 250; and Oceania, about 60.

The highest diversity of orchid species occurs in tropical areas of the globe, notably on mountain areas, which are natural barriers that insulate the several populations of plants. Islands also favor development of species but unlikely mountain areas, islands do not favor diversity that much because, unless the island is large enough to have a variety of climates, what is more common is to find a high number of few endemic species that do not exist anywhere else. Exceptions are large islands as Borneo, New Guinea, Madagascar and some other, where the diversity is enormous, these have both a high number of endemic and wealthy of different species. Therefore, some of the main areas in the world noted for having a large number of species are the Islands os Southeast Asia, the mountain areas of Ecuador and Colombia and the Atlantic Jungle along Brazilian coastal mountains, where there are more than fifteen hundred species. Other important diversity areas are the mountains of Mesoamerica and the ones south of Himalaya, in India and China, besides the southeast of Africa, particularly Madagascar. Ecuador is the country where the largest number of orchid species is reported, up to 3,549, immediately followed by Colombia, with 2,723, New Guinea, 2,717, and Brazil, with a total of 2,590. Among others, Borneo, Sumatra, Madagascar, Venezuela and Costa Rica, are countries with high number of species.

Habit
Orchids adapted to the most different environments. They may be terrestrial, growing on grass fields and savannahs among the grass, or on the soil of shady forests, epiphytic over trees or bushes, close to the soil sheltered from bright sunlight, or clore to the top of the trees and cacti, exposed to strong sunlight; they may be lithophytes growing over rocky soil or directly on the stones, they may be psamophytics along the sand of the beaches, some are myco-heterotrophs living in association with fungi, a few species are achlorophyllous holoparasites, or, rarely, paludicolous, in marshes and swamp areas. There is also an extreme case of a buried species from Australia whose only the flowers occasionally emerge straight from the soil.

The most common kinds of orchids in each of these areas are highly variable. On tropical regions, where the light and humidity are high, yet the competition for light with tree species is strong, the orchids tent to be predominant epiphytical, however, many species of terrestrial species, able to thrive without high amounts of light do exist too. Looking for light, under the shadow of trees up to forty meters tall, this herbs grow over their branches and stems, at diverse heights, according to the necessities of each species. Their roots, exposed to the air, obtain most ot the nutrients from decaying material that accumulates around them, from the rains that washes the tree leaves from above, or from the air dust. Orchid roots are recovered by a spongy tissue called vellamen. Associated with the velamen, most of orchids host a fungus known as Mycorrhyza that helps on decomposing of organic material breaking them into mineral salts, making easier their absorption by orchids. In extreme conditions, orchids may to some extent, absorb water and nutrients thorough the pores on their leaves, leaving to the roots only the function of sustaining the plant attached to the substrate. No orchid is a parasite of other plants, what means their presence never damages their hosts, despite, in exceptional cases, some tree branches may not be strong enough to sustain the weight of a large colony and may end broken. There are many terrestrial orchids on tropical areas too, although, differently form the ones from temperate regions, many may keep growing almost constantly during most of the year. The great amount of organic material available on forests soil favors the occurrence of few myco-heterotrophs species of orchids without chlorophyll, which obtain all their nutrients from substances rejected by the processing of decomposing material by fungi associated to them. All epiphytic orchids are myco-heterotrophic during germination and seedling period and many adult plants may continue to obtain some nutrients from their mycorrhizal fungi.

In regions where the climate is colder, where the grass fields are most common, or in dryer and rockier areas with small bushes, orchids are basically terrestrial plants with buried roots, sometimes developed into tubers which enable them to resist winter and snow, ot to long droughts and occasional fires. The snow might frost epiphytic species without sheltered roots to store the nutrients needed to shot a new growth in springtime. Also the fires would entirely burn epiphytic species. In this areas subject to most defined seasonal climate, the plants normally have a distinct period of dormancy while often their aerial segments die to avoid damages to their physiology due to extreme droughts or cold.

Some species are considered endangered of extinction in the wild, both because of extensive collection, as due to the cut of forests for agriculture and even by the utilization of defoliating substances during wars from the past. Surprisingly enough, the majority of the endangered species are included among the most common under cultivation and the more frequently commercially grown. Most of really rare species are not found on the lists of endangered species because they have no commercial value and low interest because of their tiny flowers or difficulty of culture. Ordinarily, for the same reasons, governments do not sponsor any surveys about the existing population of these in the wild and the few ones that exist are just occasional or made by private or academic researchers.

Other important fact to consider against extinction is that each orchid fruit can contain hundreds of thousands seeds, and that the existence of two or three individuals under culture may produce, in a few years, a fantastic number of plants, making the extinction threat of an orchid much different from the same threat to an animal, that just have one or few cubs each pregnancy.

Growth and blooming habits
Orchids growth occurs in several different patterns, it may be continuous, when orchids grow more or less constantly along the year, or seasonal, when they have definite periods of growth and rest according to the seasons. They may be sympodial, when the soot a new growth from the base of a previous one, in this case the old growth is fully developed and will not grow any further; or monopodial, when they continuously grow up shooting new leaves from a central stem. In some cases, as in Scaphyglottis and some Pleurothallidinae genera they grow both from the base and from the top of older pseudobulbs. Some orchis grow forming tight specimen plants, other are very spaced as some Rodriguezia species which have their pseudobulbs sometimes spaced for fifty centimeters. Vanilla species may have stems up twelve meters with spaced leaves climbing over the trees. Some always grow up, other show pendent habits and grow down hanging in the air from the branches of the trees. Depending upon the environment condition, certain growth forms are predominant. In tropical areas, continuous growth is more common, despite there are also a high number of species of seasonal growth. In areas subject to droughts or intense cold, the seasonal growth is the rule. Monopodial orchids usually grow continuously, sympodial, ordinarily show certain seasonality.

Orchids blooming habits are much varied. Most species just bloom once a year is a certain season but there are many exceptions to this rule. Flickingeria species may bloom many times a year. They usually do few days after a cold rain during a warm day occurs. Other species, as some Epidendrum and Paphiopedilum bloom continuously for months. Disa species may need fires, and some Coelogyne, cold, to start blooming, therefore, years may pass before they bloom. Many Dracula species bloom randomly anytime of the year.

Morphology
Among all the characteristics that distinguish Orchidaceae, very few are shared by all its species. This happens because orchids are a recent family in active evolution. Some groups of orchids derived from the core group of original ancestors very early, possibly during their first evolutionary steps, and have retained many of their qualities, while others remained constant and derived much later. As the orchids have shown an enormous capacity of adaptation, this has led to an equally huge number of variations and species.

All orchids share, at different degrees, a number of characteristics that are not common in most of plant families, although for each of these characteristics, there are abundant examples of orchids without them, however, however, some are always present:
 * The presence of the column, a structure originated from the fusion of the flowers male and female sexual organs;
 * Pollen frequently aggregated into cartilaginous structures called pollinia;
 * very small seeds, almost without nutrients, formed by few cells, which only germinate when certain fungi are present;
 * Flowers of lateral symmetry, not radial, composed by six segments, three external ones called sepals, and tree internal, called petals. Among the later, one is different, called labellum, which normally are responsible for pollinators attraction to the column, and participates actively of pollination mechanism.
 * Orchid flowers usually are presented inverted from the natural position due to a process known as ressupination, when during the bud growth, the ovaries twists itself 180º;
 * Most of epiphytic species have their roots covered by a spongy tissue called vellamen;
 * The life span of an orchid is undetermined because they grow indefinitely, continuously or during short annual periods, in theory for unlimited time. Few is known about the age an orchid can reach but there are records of their longevity both from the oldest specimen under culture at the Royal Botanic Garden, which is older than two hundred years, as for a plant that belongs to the Círculo Americanense de Orquidófilos, already cultivated for more than one hundred years.

Roots: Orchids have no primary roots, that are main central roots where secondary roots grow from, but only the secondary roots, which start directly from the stem and, occasionally, from other secondary roots. Frequently the roots act as a storage of nutrients and water, helping the plant to retain and accumulate nutritional substances that deposit on their bases. In some cases the roots have chlorophyll organs capable of carrying photosyntheses during the periods when the plants loose their leaves. Their roots show varied thicknesses, from highly thin to extremely thick. Roots structure is highly variable among orchid genera, according to the way and the places they grow.

The epiphytic species generally present robust roots, cylindrical when aerial, which become flatter after attaching to the substrate. They are frequently recovered by the vellamen, which is a thick spongy tissue that is very important to enable orchids to quickly absorb high quantities of water from the rains and even humidity from the air. Some species, particularly to ones of subtibus Catasetiinae behave as if they were pneumatophorous, with plenty of thin roots growing up forming a sort of wig. The reason for this roots do so is to catch leaves and sediments that shed from above during the rains.

The terrestrial species normally bear some roots thickened into small or large structures that resemble tubers, which may be spherical to elongated cylinders which act as storage of water and nutrients, replacing the role carried by the pseudobulbs usually present on epiphytic species. Occasionally these tubers split from the mother plant originating new plants. Some Australian species of the subtribus Caladeniinae have almost no roots, they are only constituted by a small ovoid tuber and nothing else. On the other hand, the tubers of the Brazilian Cleistes are thin and delicate measuring more than one meter, spreading in several directions. Collecting this species is almost impossible for their tubers will break causing the death of the plant.

The roots life time varies according to environmental conditions and generally is inferior to the stem life time. New roots usually shot during or at the end of each plant vegetative growth period. Despite this is not the primary nutritional source of orchids, they usually benefit from a kind of symbiosis or association with a fungus called Micorrhyza lodged on the vellamen exterior cells of their roots and excretes several nutrients directly absorbed their roots.

Stems: On epiphytic species of sympodial growth the stem usually is formed by two segments, one of them, called rhyzome, shows reptant growth, which means it grows along the substrate, some terrestrial orchids also may have a rhyzome. The other segment is aerial and may or may not be thickened into a structure called pseudobulb, which acts as water and nutrients storage.

The rhyzome can be short, then the orchids assume a highly dense appearance. This type of growth is called cespitous growth and is very common among orchids. The orchids of genus Bifrenaria always present this type of growth. When the rhizome is more elongated, the plants assume more of a climber and somewhat messy appearance when the rhizome is ascending, the rhyzome sometimes spaces their pseudobulbs by more than half a meter. Acacallis and Rodriguezia are examples of this sort of ascending growth. When the rhizome is more malleable the orchids usually become pending. Loefgrenianthus is a pending orchid. In some species of Pleurothallidinae, particularly on the group of Acianthera prolifera, the rhyzome is very thick for it the species of this subtribus do not have pseudobulbs, here replace by a thin stem called ramicaul which is not capable to retain water enough, therefore the rhyzome took over this responsibility.

The aerial segment of the stem, the pseudobulb, is very characteristic of orchids family. Observing the pseudobulbs size and shape, experienced growers may recognize most of the genera. This is because pseudobulbs are highly variable with countless shapes. the may be fat and large as a papaya ins some Gramatophyllum species, or thin and long as sugarcane in some Epidendrum. They may bear one leaf, as many Cattleya, or tens as some Dendrobium. Some Bulbophyllum have small pseudobulbs exactly the size and shape of rice grains. The ones of Psychopsiella are flattened towards the substrate as if someone had stepped on them. Some large Bifrenaria look like exactly as a hand of bananas. Pseudobulbs also vary in color and can be hidden among the leaves.

In some epiphytic genera, particularly the ones related to genus Huntleya, the secondary, or aerial stem, is reduced to an inconspicuous node which originates the leaves. Sympodial orchids usually show seasonal growth and new secondary stems are added each period.

On epiphytic species of monopodial growth the stem is formed by the aerial segment only. It may be erect or pendent and its extremity grows continuously forming new leaves and occasional lateral roots or new growths along the stem. The stem of this kind of orchids is never thickened into pseudobulbs, however their leaves and roots ordinarily are comparatively thicker than the epiphytic ones, as they frequently help retaining water and nutrients.

Terrestrial species may or may not have developed stems and these, different from epiphytic orchids which always show perennial stems, may be partially or entirely deciduous. Usually in these cases they are not really stems but pseudostems formed by the leaves. Some terrestrial orchids of genus Epistephium and Selenipedium present very long stems, which sometimes reach more than six meters of length, there are the tallest orchids that exist.

Leaves: The majority of orchids have leaves of longitudinal parallel venation with hardly visible crossings. Usually arranged in two alternated opposed rows, both sides of the stem. Many species have only one pseudo-terminal leaf and one aborted growth. Their shape, thickness, quantity, color, size and the way they grow is highly variable. The shape of their blades can be circular, elliptical, lanceolated, oval, linear, oblong, spatulated, besides endless intermediate forms. The leaves apex may be rounded, accuminated, acute, thin or thick, pointed, radial, or uneven. Their edges are ordinarily smooth, partially curved, hardly ever denticulated. The structure of the leaves may or may not show a petiole, with a variable number of longitudinal parallel nerves, very visible as in many Coeogyne and [Stanhopea]] species, or almost imperceptible. The leaves thickness goes from very thin and malleable, as Stigmatosema species or fleshy, firm and breakable, as Cattleya ones to entirely succulent as Leptotes. Ordinarily bearing the most diverse shades of green, leaves colors may also be completely different according to the faces, from red to dark brown, gray tones, blueish, whitish or yellowish. Some species have stained, striped or doted leaves with several different colors. Generally their surfaces is glossy, occasionally they may have a dull appearance or even look like if recovered by white dust, like in Euchile of completely hairy as all species of Trichotosia.

Some species are lacking chlorophyll. The majority of species keep their leaves during some years, but some loose them immediately after their seasonal growth period and other when environmental conditions are adverse. There are also some genera, like part of Campylocentrum species, whose leaves are just rudimentary, giving the impression they have only roots and eventual flowers. In these cases the roots usually have chlorophyll and are responsible for photosyntheses.

Inflorescence: Orchids inflorescences, according to the species, may have from one to some hundred flowers. They may be apical, lateral or basal, racemose or paniculated, forming branches, corymbes or umbellas, erect, arching or pending, with simultaneous or successive flowers, which can grow along the inflorescence or always from the same spot. Some species show perennial structures that are a sort of modified stem used only for blooming during several years, as it happens with some species of Masdevallia and all species of genus Psychopsis. The flowers generally have bracts at their bases. These bracts are variable in size, frequently highly reduced, may also be very large, looking to be part of the flower, as in some Cyrtopodium or sometimes even bigger and more attractive than the flowers, which remain partially hidden by them, as in some Eria. The inflorescence from genus Dimorphorchis may be five meters long, with two different kinds of flowers spaced almost one meter each. Octomeria inflorescences just measure a couple of millimeters. The inflorescence of some orchid species grow down, thus when these are cultivated, they appear through the holes at the bottom of the pot.

Flowers: Among all plant families, orchids possibly are the ones of the widest spectrum of floral variation. Generally they have hermaphrodite flowers, but besides those, some genera in subtribus Catasetiinae may have exclusively male and female flowers, occasionally showing a third type of flowers that can be hermaphrodite at several degrees, sometimes resembling more male, sometimes more female. Interestingly enough, when these genera with dimorphic flowers produce hermaphrodite ones, despite they are fertile, apparently there is no natural pollinator for them.

The size of their flowers varies from one millimeter up to twenty centimeters, or even the double if the calcar of some orchid flowers is included. Their colors range from almost translucent to white, greenish shades, pale pink or bluish to very vibrant colors as yellow, orange, red and dark purple. Many are multicolored.

The flowers normally show bilateral symmetry, bearing six tepals split in two layers, three external called sepals and three internal denominated petals. Both the sepals and the petals are highly variable in shape and size, and occasionally are partially or completely fused. One of the petals, denominated labellum, or informally as lip, always is differentiated, normally expanded but sometimes smaller than the rest of the segments, it may be very simple resembling one of the petals or may have calli, keels oe warts, highly variable and complicated shapes with diverse and contrasting colors. In many genera the labellum shows an hollow tubular appendix at the base, called calcar, or a nectary close to the area where it is hinged or attached to the column. Observing the structures and patterns of the labellum is one of the most simple ways to recognize each of the orchid species.

Their reproductive organs, (androceu and gineceu), are reduced and fused into a single central structure called column, gymnostem or androstyle. The number of estamen varies among the subfamilies: Apostasioideae has two or three; Cypripedioideae has two, with the central estamen modified; the other subfamilies have just the central stamen is functional, and two other are atrophied or absent. Also observing the characteristics of the column is important to correctly identify a particular species.

The pollen grains usually are compressed or agglutinated into waxy pellets called pollinia but alternatively may be grouped in mealy or paste-like doughs, or, hardly ever, loose. The pollinia are hinged by a thin connective rod structure called caudicle or stipe, according to its morphology, attached to a viscous disc called viscidium, hold in place by a thick liquid produced by the rostellum. Most of epiphytic species has a little helmet protecting the pollinia denominated anther cap. The stigma normally is a cavity located at the column, partially filled with the same thick liquid the rostellum produces, where the pollinia are inserted by the pollinator when it visits the flower. The ovarium usually is composed by three chambers and bears up to circa one million eggs.

Fruit: Almost all orchid have capsular fruits. They are clearly different in shape, size and color. The epiphytes bear much thicker fruits with fleshy walls than terrestrial species which present them thiner with more delicate walls. Generally they are triangular, somewhat or highly rounded, with a variable number of keels, from three to nine. Some are smooth, other are wrinkly or covered with warts and protuberances all over their surfaces. The fruits result from the thickening of the ovaries located at the base of the flowers, which is also ordinarily formed by three chambers. When ripe, the fruit opens in three or six windows or almost entirely along its length, although always remaining attached to the inflorescence. Most of the seeds soon fall down, laying among the roots of mother plant, the rest is taken by the wind for long distances.

Seeds: Almost all orchids present light tiny seeds, formed by a a small number of covering cells protecting an embryo. One plant produces hundreds of thousands seeds each capsule. Contrary to most plants, which generally produce endosperm capable of feeding the embryo during their initial period of development, orchids use a symbiotic process with the fungus Micorrhyza, which excretes the nutrients necessary to nourish the young plant decomposing the material gathered close to the seed. As soon as the embryo is capable of carrying photosyntheses, this becomes responsible for the nourishment of the plant and the Micorrhyza is not necessary anymore, however, some species of myco-heterotrophs orchids will never be capable of fully carrying photosyntheses thus remain dependent upon this fungus for all their lives. Some species of orchids, as Bletilla do show some amount of endosperm. Few orchid species have comparatively large seeds, mostly the members of the subfamily Vanilloideae.

Taxonomy
Orchidaceae is considered one of the largest, if not the largest, family among all plant families. The number of species is close to 25 thousand, corresponding to about eight percent of all seed plants. The exact number of accepted species is four times bigger than the mammal species and two times the birds. These impressive numbers do not take into account the huge amount of new hybrids and varieties produced by orchid growers every year. Moreover, even today, hundreds of new species are described yearly, both because of revisions of long established genera but whose species were not well determined, as due to new species discovered in nature. Only in 2008 the International Plant Names Index registered more than four hundred new descriptions.

The orchid family was established when Antoine Laurent de Jussieu published his Genera Plantarum, in 1789. However, before Jussieu's classification, Linnaeus already had described eight orchid genera which, nevertheless, did not form a family. At the time all epiphytic species belonged to the genus Epidendrum. Other genus described by Linnaeus was Orchis, a greek word refering to the shape of two small tubers that the species of this genus show, which resemble testicles. As this was the first orchid genus to be formally described, from it derived the name of the whole family.

Since Orchidaceae was proposed, the research on its species has not been interrupted. Their classification passed through numberless revisions and the amount of known genera they are divided has been increasing throughout the years, now reaching more than eight hundred. Their exact number is not known because there is no consensus about the best way of splitting the genera. According to each reference, the list of accepted genera are diverse and the total number much different. A good example is comparing the number of genera published since 2002 to classify species before subordinated to genus Dendrobium, about thirty, and the number of these which are actually accepted by the database of the Royal Botanic Garden, three or four. The most recent trend is the classification based upon genetic, or molecular information called Phylogeny, which in theory reflects the evolutionary relations among each one of the species, groups of species, genera, and so forth. However, this system is comparatively new and not all researchers fully accept it, many still basing their conclusions mostly on morphologycal diagnosis. The debate is lively held on both fronts. One of the defenders of Phylogenetics is Mark Chase, who places morphology on a secondary level, Among the morphologists one of the most noted is Carlyle August Luer, who since 1978 dedicated to study the species of subtribe Pleurothallidinae and thinks that phylogenetic should be regarded only as an extra tool for now. Luer has described about three thousand new species of orchids.

Orchids study has appealed to several noted Botanist and Taxonomists through the ages. Since the modern system of classification was established the most noted ones to dedicate to this family in the past were the English Botanist John Lindley, possibly the most important of all, as he described thousands of species and hundreds of new genera still accepted today, however, not denying his importance, almost every orchid was new at his time. After Lindley, two German Heinrich Gustav Reichenbach and Rudolf Schlechter, also described thousands of species. Moreover, Schlechter was responsible for the first systematic classification of orchids used till few decades ago. Among the living Botanists possibly the most noted names are two American, Robert Dressler who guessed most of relationships among orchids, later proved correct by Phylogeny, and also established the bases of the orchid classification used today, and at last, Carlyle Luer, mentioned on the former paragraph.

Orchidaceae is a family passing through an active cycle of evolutionary development. Traditionally, Biology considers the species concept as a group of beings that can breed producing fertile descendants. Orchid species are slightly different because they do not fit well in this concept. Not only most of the species can interbreed with several other producing fertile descendants, as most of the genera that belong to the same subtribe can do too. It is not uncommon to encounter natural hybrids between different species and genera in the wild, and although almost all these plants are fertile, the are not more common just because as orchids are highly adapted to their pollinator, these hybrids may occur by chance and their particular resulting morphology are not really adapted to the existing pollinators. There are some rare exceptions, when these hybrids are result of breedings of two closely related species and still can be pollinated by the same pollinators of parent species. When this happens it is more likely that along the years a new species can appear. This may be the case of Cattleya × mesquitae. It is a natural hybrid discovered in 1996 in Goiás State in Brazil. We know know that this species is a result of a high degree of interbreeding of Cattleya walkeriana and Cattleya nobilior. As the result of this breeding is pollinated by the same agents of its parents, the crossing has been occurring again and again between the three species from the area along the ages, thus one of the original parents cannot be found there anymore. All original plants have crossed and faded. Today we know Cattleya × mesquitae is a hybrid because similar plants have been produced by artificial breedings. Lou Menezes, its describer, claims that this species is so ancient that they have even evolved in nature, developing a fragrance that is not present on the hybrids artificially produced. This is one of the ways a new species can appear in the wild. Cases like this are not uncommon among orchids, therefore many species are hard to separate exactly because they result of different degrees of breedings between closely related species in a given area. Furthermore orchid hybrids produce variable descendants that may be closer to either one of the parents or an intermediate mixture of both. It is also possible that one day many species described by Botanists may be proved to be in fact natural hybrids long established in nature.

The definition of each species sometimes is complicated even further because many groups may be isolated and show subtle differences that some taxonomists may think are enough to establish independent species while other may think these are just natural variations of populations separated for long time but not yet important enough to justify the establishment of another species. Therefore the exact number of orchid species to be accepted by the scientific community is highly variable according to each reference. Today many taxonomists would rather classify these groups of species as superspecies or complexes of cryptic species. In these cases the differences between the extreme variations of a group con be clearly seen, but there are so many intermediate forms that placing exact limits between several species is almost impossible. There are many examples of these groups, as such the ones of Brasiliorchis picta, Anacheilium vespa, Heterotaxis crassifolia, and countless others.

The orchid family is formed by five subfamilies:


 * Apostasioideae Reichenbach
 * Plants with mealy or paste-like pollen, which ordinarily are not aggregated into pellets, called pollinia, with two or three fertile long anthers, leaves with stealthing bases, elongated staminodium and labellum similar to the petals. It is the smallest subfamily, not split into tribes but only two genera and sixteen species from southeast Asia;


 * Cypripedioideae Lindley
 * Plants with mealy or paste-like pollen, which ordinarily are not aggregated into pollinia, with two oblong or oval anthers, leaves with stealthing bases, shelter-like staminodium and labellum generally saccate. This subfamily is split in five genera and 170 species spread though the world temperate areas, few encountered in tropical America;


 * Vanilloideae Szlachetko
 * Plants with mealy or paste-like pollen, which ordinarily are not aggregated into pollinia, with one fertile incumbent anther only and leaves without stealthing bases. It is divided into two tribes, fifteen genera and 250 species spread throughout the humid tropical and subtropical areas of the world, and east of United States of America;


 * Orchidoideae Lindley
 * Plants with coherent pollen forming pollinia, with one fertile anther, erect or bent back, and convolute leaves but not very plicate, roots ordinarily fleshy or tuberous. This subfamily is formed by six tribes and several subtribes, encompassing 208 genera and 3630 species distributed along almost all over the world, except the dryer deserts and polar areas;


 * Epidendroideae Lindley
 * Plants with coherent pollen forming pollinia and with one incumbent anther only, or with the anther bent back, but then with clearly plicate leaves and roots hardly ever fleshy. This is the largest subfamily, formed by several tribes and subtribes, more than five hundred genera and about twenty thousand species, distributed along the same areas of Orchidoideae, despite there are also buried species living at the deserts of Australia.

The division of the orchid species by genera is highly irregular. There is a great number of genera with one species only and some huge genera bearing more than a thousand. Despite many or these large genera are going through revision and breaking into smaller and handier genera many are not. We mention some of there larger genera as they were classified at the end of 2007: Bulbophyllum with almost two thousand species; Lepanthes, Stelis, Epidendrum, Pleurothallis, and Dendrobium with more than a thousand; Oncidium, Habenaria and Maxillaria bearing circa seven hundred; and Masdevallia, with more than five hundred.

Pollination
Because of their reproductive structure, orchids necessarily need help of external agents to carry the pollen to the female organ of their flowers as the pollinia are too heavy to be taken by the wind and the receptive segment of their female organs are not sufficiently exposed to receive it. The orchids are pollinated by agents as diverse as bees, butterflies, diurnal and nocturnal moths, beetles and hummimngbirds.

The majority of other plants flowers try to attract pollinators offering rewards, mostly in form of food. Orchids, being plants that live from so sparse resources, need to be very economic so they developed other techniques of attraction which hardly include these food rewards. The most usual trick is the mimicry of any form that may interest to the insects and other agents, such as color, fragrances, or wax. They have also adapted their shapes in a way to ensure the pollinators to carry the pollen when they visit the flowers, although they adapted so perfectly that only the right visitor will adjust to the flower mechanics. Other visitors will not take the pollen away. This happens because all pollen is aggregated in masses that can only been taken once, thus each flower has one chance of pollination only. The labellum also helps a great deal on the process because they developed a variety of structures aiming to place the pollinator on the exact position to ensure that the pollinia they carry will reach the right spot into the flower stigma.

Orchids use the most fascinating strategies to promote pollination. Some of their flowers may show very interesting shapes. Orchids classified under the European genus Orchis show the labellum color and format, ornamented by bristles in such a way that exactly reproduce the females of a particular species of bee, moreover they produce the same pheromone she does, thus the male bees are attracted to a copula, taking then the pollinia with them, which will be delivered to the next visited flower.

Other orchids, as the ones of the African genus Angraecum, have white or light green flowers, the right ones to be most easily seen during the night. These flowers produce nectar in extremely long tubes located at the base of their lips, in a way that only certain night moths bearing equally long proboscids may reach it. When the look for the right position, the moths touch their heads on the anthers, in this activity the pollinia become firmly attached to them.

Orchid flowers of the genus Coryanthes, continuously shed a liquid that falls into a bowl formed by their lips. Trying to collect this liquid the insects fall inside the lip and they just can exit through a tight opening. When passing through it they take the pollinia away on their backs.

The labellum of the flowers of Bulbophyllum species are hinged do the column by a so delicate structure that it allows their lips to balance with the wind in a mimicry of the insects movement.

The flowers of genus Catasetum may be male, female or hermaphrodite. The male flowers are much more attractive than the female ones and have two highly sensitive antennas close to the labellum. When these antennas are touched, they eject the pollinarium as strongly that, when they do not reach the insect, they cover almost two meters in a fraction of a second.

Some orchids, instead of nectar, secrete fragrances. Some of these fragrances also fake fragrances of other species trying to make the insects to believe they will he rewarded by the orchids as they are by the other plants. This is why the perfume of coconut is the one of Maxillariella tenuifolia, Epidendrum rondoniense smells exactly as red berries, Christensonella subulata is like watermelon and so forth. On the other hand some orchids try to attract a completely different type of insects so they smell like dead meat. Some have different fragrances during the morning and during the night. Some are perfumed just at certain times of the days when the right insects are active.

Some orchid species get self pollinated easily. This process is called cleistogamy. At last, examples of pollination strategies employed by orchids are countless. Other pollination mechanisms will be discussed along the orchid species and genera articles.

Evolution
Until recently, the time frame when orchids became separated from the ancestrals they share with the other Asparagales was far from an exact guess, however the discovery of their first fossil in the Dominican Republic in 2007, make the former estimate that they would be 45 to 50 million years old go back to the recent estimate of 84 millions years. The recovered fossil is from a terrestrial species much similar to species today classified under the genus Microchilus. However the exact appearence of the flower is just implied only their pollinia were found, attached to the back of a bee trapped and conserved in a piece of amber ever since.

The pantropical distribution of certain primitive genera such as Corymborkis and Vanilla seems to indicate that this occurred before the continents became enterely separated. Nevertheless the most active evolution of orchids seems to have occured after this separation when the several tropical areas where already well established, about 55 million years ago. It is accepted also the pressumption that by this time the five orchid subfamilies were already separated and their ancestral species well developed.

The epiphytism of orchids is a result of their adjustment to the environmental conditions present along their evolution and not constitutes itself in an ancestral characteristcs. The development of vellamen, reduction of the seeds size allowing them to be spread by the wind, and their association to Micorrhyza should have occured at the same time they migrated from the soil to the trees. Several characteristics modern orchds share seem to indicate that their primitive ancestor may have been a small plant of sympodial growth, delicate rhyzome, fleshy roots, folded leaves and terminal inflorescences.

Their flowers evolved from a lilly type of flower, slowly adapting to each of their pollinators, geting rid of superfluous structures and adding structural elements to ease pollination by particular agents. The inferior petal, because was the landing track to the insects, became adapted and progressively different from the other two petals, becoming more and more attractive.

The orchids and the man
Orchids have fascinated the men form more than 25 hundred years. In the past they have been used in healing recipes, as aphrodisiacs, for decoration, and occupied important role in supersticion. There are several references on Internet to the interest the Chinese philosopher Confucius had for them, although the majority of this mentions, where he remarks the properties of their fragrances to which he attributed the character Lán, meaning beauty, softness, love, purity ans elegance, comes from texts published by his followers and admirers. There is at least one reference to orchids he wrote in The School Sayings of Confucius, however, even this possibly is an apocryphal text. Nevertheless, the fact his followers attributed to Confucius the most diverse citations about these plants only confirms the interest they arouse at the time. China has a long history about the appreciation of these flowers. Orchids are cited by ancient literature and pictured by Chinese art since the tenth century BC, paintings dated the early Song Dynasty time, between 960 and 1127, survived to our days. Yet, recent investigations revealed that the culture of Cymbidium started just at the end of Tang Dynasty, between 860 and 890, and not at Confucius time as is was previously believed. Possibly the first publication exclusively about orchids is a monography about their extensive culture at the end of Song Dynasty, between 1128 and 1283. In this work one can imply their culture was well established in China at the time.

In Europe there are registers from the Greek Classical Period of Theophrastus of Lesbos, circa 300 BC. On his work Historia Plantarum, volume 9, he describes a plant with two little buried tubers to whom he refers as Orchis, corresponding to the word testicles, possibly a specimen of Anacamptis morio.

Before the spanish concquered Mexico the Tlilxochitl fruit, a species of Vanilla, was the mos cheerished among the Azstec spices. This poeple praised also the Coatzontecomaxochitl, Stanhopea, as sacred flowers they cultivated on their gardens. The Aztec also used some orchid species for glue production. After 16th Century several works were published in Europe: Leonhart Fuchs in Historia Stirpium (1542), Hieronymus Bock in his Annotations volume 2 (1546), Jacques Daléchamps in Historia Generalis Plantarum (1586). After the publications of Species Plantarum by Linné, in 1753, the publications dealing with orchids became progressively abundant.

Previously to the introduction of exotic species in Europe, orchids were cultivated as garden plants for long time. The first exotic orchid to be taken to Europe was a specimen of Brassavola nodosa which arrived on the Netherlands in 1615. In 1688, disembarked the first Disa uniflora brought form South Africa.

Probably because of their supremacy, several important collections gathered in England during the 19th Century. In 1818, the first plants of Cattleya labiata, discovered in Brazil, were delivered causing great sensation and boosting even more the interest for the tropical species of orchids.

The advent of their first showy hybrids, at the end of 19th Century, slowed down for some decades the interest for new plants from the Tropics, until the scientific interest in describing new species at the start of 20th Century, increased the plants collection again, to be sent to Europe, mostly to Botanic Gardens and amateurs interested in renovating their private collections.

The offering of hybrids is increasing constantly and the modern techniques of seedling developed so much that their prices, usually regarded as expensive in the past, is going down. The artificial reproduction of plants naturally selects the ones more adapted to different climates thus, species that were once very hard to grow outside their wild habitats are becoming progressively easier to grow at home. The offering of rare wild varieties of natural species, with selected colors and shapes, has made comparatively easy to any one to afford plants previously available only to millionaires. In a few years any highly desirable plant can be produced by thousands. It is noticeable the example of Phragmipedium kovachii, extremely rare species, only few plants just recently discovered, in 2002, today is already becoming common in private collections around the world.

Uses
Despite the high number of orchid species, few are the ones grown for their utility. Besides the already mentioned Vanilla, widely used as flavoring, some other species are locally used for the same purpose, for instance fragrant species of Jumellea are used to flavor tea in Africa, and Vanilla is also locally used with tobacco. In Turkey the tubers of Anacamptis morio are a component to made an ice cream called salep. During the 19th Century Cyrtopodium pseudobulbs were used as home made glue in Brazil. The true value of orchids today comes from cut flower production, mostly hybrids of the genera Phalaenopsis, Cattleya, Dendrobium, Paphiopedilum and Cymbidium. The same plants are also sold for house decorating.

Thailand has been working on development of extensive production of orchid flowers as export goods to large cities around the world. In 2001, they exported more than 3 million plants sold for circa 40 million dollars. Ever since the Agriculture department of Thailand recognized the potential of this culture and is working to increase the quality and attractiveness of their clones granting certificates to the best producers.

In Netherlands, 216 registered growers produce high amounts of hybrids for whole sale. In the United States it is estimated that in 2003 potted plants market made about 121 million Dollars. Today the wholesale market o mercado atacadista is supplied mostly by seedling flasks to be locally cultivated for future sales. From 1991 to 2001 greman production of micropropagated orchids jumped from two and a half million to twelve million plants, mostly hybrids, particularly of Phalaenopsis.

Culture
Because the orchid species are so diverse and come from so varied environments and climates, it is impossible to have basic directions of culture for them as a whole. The first step to succeed on orchids culture is trying to identify the species. Usually, the most important recommendation to newbies who intend to seriously grow orchids is to never buy an orchid without an identification tag, unless they are intended just for home decoration. The reason why the identification tag is important is because generally it is the best and sometimes only, way to learn how to grow each one of them. When orchids are natural species, it is always possible to identify them. Some ways to do so are asking to more knowledgeable friends or experienced orchid collectors, looking on books or Internet, or even joining orchid societies. Learning the name of the species means learning where it comes from so their original natural conditions may be reproduced, deciding what is the best amount of light, humidity, temperature, watering, which is the best type of substrate and drainage, if they should be potted or mounted, and what is the resting period regime of the plant. The most common error is potting orchids on mud. Hardly orchids will thrive on this kind of substrate as circa 70% of orchids are epiphytes which means need their roots dry few hours after they were watered. There is no mud over the trees where they live. there are many choices of substrate mixes available on stores. Another common mistake is having a plate under the pots to prevent the water to spread around. Plates also result in excessive humidity and unless this orchid is one of the few that actually like lots of humidity, it will be dead in a few months. Most of the orchids need their roots to get completely dry before being watered again.

Usually orchids are regarded as delicate plants that are very hard to grow. This is not true. As mentioned before orchids can take a lot of adverse conditions and the are actually prepared for that, sometimes they even need them. It is interesting to notice how some orchids, when are very well cared, grow beautifully but never bloom. this is the case with several species of Dendrobium which need a very dry period at the end of their resting time. During this drought their pseudobulbs shrink and the plant assumes a very poor appearance, sometimes loosing all their leaves. This seems to indicate that the plant feeling the adversity gathers all its strength and blooms trying to spread their seed before dying, however, just after they bloom, it is rain time in the wild so they start to receive all the nutrients they need to live through another cycle. Some species of South Africa, among which Disa sometimes pass several years without any bloom but provided there is a fire in the area they bloom generously. Other plants need extreme cold to trigger the blooming, or just a very hot day with a cold shower at the end of the afternoon. The pseudobulbs most orchids have make them very resistant, capable to pass long time without being potted. Actually some growers never pot or mount their orchids. Most monopodial orchids from southeast Asia can live just hanging with all their roots hanging in the air. In nature they take their nutrients from the water that washes the tree leaves above them, in nurseries they take them from fertilizers. Orchid hybrids usually are stronger than wild orchid for they have mixed genes from two species and this mixture generally produces stronger individuals, which grow faster and than wild species.

Almost every large city around the world has at least one orchid society were generally congregate local amateur and professional growers. These societies have periodical reunions, sometimes weekly, sometimes monthly, where they discuss the last news, exchange experiences and orchids, show plants, learn to recognize what is desirable in plant, listen to lectures and even visit for the partying. When there are several societies in other cities nearby, they may have orchid shows open to the public and even organize championships of culture and rarity. Most countries have a main institution that is responsible for the schedule of orchid shows in the country, for setting their rules and managing the evaluating and judges selection, and keeping the records of best orchids shown as well. Two good examples of such organizations are American Orchid Society, AOS, and Coordenadoria das Associações Orquidófilas do Brasil, CAOB. Both are non-profit institutions which keep websites on Internet and are very good references to the ones looking information about the orchid societies in the area where they live.

Growing orchids in the north of United States or Europe is considerable harder than doing it in the tropical areas. Expenses to maintain small greenhouses or nurseries may be high during the winter and growers in those areas usually would rather grow smaller species so they can have more varieties in less room. Growers in tropical areas hardly have to concern with weather thus it is much more affordable and large specimen plants are more common in those collections. Orchid culture is very common in the southeast of Brazil. There are so many orchid societies in São Paulo State that every weekend there is at least one orchid show happening, and sometimes four at once, spread through the cities in the region. Attend to societies gatherings and orchid shows is the best way to learn about orchid culture.

Production
The easiest way of having a second plant form an orchid, and the most commonly used by private collectors and small profissional growers, is dividing the rhyzome or the stem. This can be done with almost any adult plant that have at least six pseudobulbs in line. In this case the rhyzome is divided and the grower has two plants with three pseudobulbs each. The best time for doing it is when the plant is shooting new roots. However, this method has being used for centuries, it is not suitable for large scale production because, as a rule, orchids produce just one pseudobulb each year, occasionally two. But orchids can also be mass-produced thanks to the fantastic amount of seeds each fruit bears and to the development of the seedlings by a process called micropropagation.

The advantages of reproducing plants from seeds, called sexual reproduction, are several, they raise the genetic diversity of the species, they naturally select the most strong and viable plants and also at some extent select some orchids that are noted for being hard to grow to thrive in a climate slight different from the one on their origin. This is because the seed that grow faster are the ones more suited to the new place. Other advantage of sexual reproduction is that, among so many different plants produced, some special varieties may appear.

As orchid seeds carry almost no endosperm, they need highly particular conditions to germinate. In nature this is provided mostly when the seed fall close to other existing orchids. Among the roots of orchids the Mycorrhyza is always present and it will support the seedling necessities of nutrients. Before the development of artificial methods of providing the conditions needed by the seedlings, for many decades, growers tried several home recipes of culture media based on tomatoes, bananas and many other ingredients cooked with agar and placed in sterile flasks with fresh smashed tips of orchid roots to add the fungus. The time an orchid takes to develop from the seed to a blooming size plat varies according to the genus but it hardly is less than three years and five or six years is the most common.

Highly rare species and varieties can also be propagated by their meristem, that is the tissue of undifferentiated cells found in zones of the plant where growth can take place, particularly gems from the stem and root apex, which can be compared to stem cells in animals. This tissue is cultivated under appropriate conditions sometimes adding hormones, and progressively cut several times. The process is progressively repeated until the number of desired clones is achieved. All the plants obtained from meristem are genetically the same of mother plant so this, different than when seeds are used, is a type of vegetative reproduction.

Most popular genera
As mentioned before, orchid culture conditions vary throughout the world, both because different genera are more adequate to each area, as vary the total expenses to maintain them according to each climate conditions. Therefore the general mostly grown in one area or country may be very rare or virtually unknown by growers of different places. For instance, Odontoglossum and Masdevallia from high altitudes in the Andes are almost impossible to grow in Brazil, where the nurseries are mostly open and subject to the weather conditions. Some of these plants like high luminosity and in Brazil there is not easy to provide high luminosity without high temperature as well. On the other hand in the North of United States these conditions are much easier to provide although growers living there will find very difficult to keep species from Amazon, as Acacallis, in constant high temperature and humidity along the year. Moreover genera mostly grown in different areas of the globe vary because not all species are easily available on every place.

Despite all these adversities, orchid collectors always keep trying to grow the species they like and some orchids genera and species, at some extent, can be found in almost all collections. Ahead is a short list of the most noted and cultivated orchid genera. The list is organized by continent of origin, not culture, and some orchids may not be grown in particular areas thus their popularity varies from country to country.


 * Europe: Orchis, Ophrys, Cypripedium.
 * Asia and Oceania: Cymbidium, Dendrobium, Phalaenopsis, Paphiopedilum, Vanda, Bulbophyllum, Coelogyne, Dendrochilum, Eria.
 * Africa: Angraecum, Aerangis, Disa.
 * America: Cattleya, Laelia, Oncidium, Epidendrum, Brassia, Catasetum, Sophronitis,  Miltonia, Pleurothallis, Masdevallia, Lycaste, Maxillaria, Phragmipedium, Encyclia, Odontoglossum, Brassavola.

Hybrids
The artificial production of orchid hybrids started more than one century ago. Fertile orchid hybrids can be crossed with other species of the same or of other genera and produce new generations of fertile hybrids. The capacity orchids have to interbreed is one of their characteristics more valuated by growers because it enables them to mix the species obtaining endless combinations of new colors and patterns. Today there are hybrids involving up to eight genera and as time passes it is likely even more genera will be crossed. The number of existing hybrids is unknown because, despite the Royal Horticultural Society, RHS, is responsible for keeping the records of these hybrids up to date, there are high numbers of hybrids produced by particular growers for many decades. Many or these hybrids were produced at a time communications were difficult most of these local producers never knew about RHS. Even now that computer make the registry so easy, most of them still ignore that these records exist. The current estimate is that these are more than a hundred thousand hybrids, but the exact number of man made hybrids will always remain a supposition.

According to the rules of International Code of Nomenclature for Cultivated Plants, ICNCP, hybrids of species belonging to the same genus always take this genus name, for instance, the result of breeding two Cattleya remains a Cattleya. When two genera are used, a new genus name is created with parts of each original ones, for instance, the hybrid of a Laelia and a Cattleya is a Laeliocattleya. When there are three or more genera involved, the producer may choose any name he wishes for the resulting genera, provided he follows few rules regarding names sufixes and that no other name had been previously registered for the same genera crossing.