INTRODUCTION

The Orchidaceae family is home to more than 30,000 flower species. Scientists suspect that there are more species in the topical areas of the world. Thus, it is by no means their rarity that makes them the center of attention for thousands of common people and has aroused so much interest in them.
What is it then that makes Orchids so interesting?
As a start, we mention the beaury of some of the orchid flowers. Not all of them are beautiful, but there are cases that an orchid can be worth more than 50000 usd. On the other hand, there are some products of major financial importance, eg. vanilla or salep, extracted from orchids. So, there is much to profit from these flowers and this alone could justify man's interest in them. But this is not all! There are more interesting facts about Orchids and their biology that rightfully put them in the center of our interest.

1. The Orchid flower
The orchid flower is bilaterally symmetrical. This means that every orchid flower can be divided on a vertical plane to produce two identical halves that are mirror images of each other (zygomorphy-please refer to photo). They are not alone to share this feature, other plant genera (e.g. Scrophulariaceae) as well have this type of flower. All of them are most attractive to the human spirit because, as some researchers maintain, they are similar to our own face, which also shows a billateral symmetry. It seems that contact of higher quality is made between an orchid and a human looking at each other's "face".
All orchid flowers consist of three sepals and three petals. The term Tepals covers both petals and sepals. The sepals and the petals can be similarly decorated, sometimes heavily so, or altogether dissimilar. One of the three petals, named the labellum or lip, is especially modified to act like a landing spot to help the flower get pollinated by luring, traping, or deceiving the pollinating insect, fly, bird, gnat, moth, butterfly, or even humming bird. Often in these cases the lip looks like a single, or multi-lobed structure that is decorated with ridges, bumps or tufts of hair. In this game, there are no other rules but the survival of the fittest. The reproductive parts of many orchid flowers, together with the especially modified labellum, are shaped, scented and colored to look like the kind of insect they aim to attract. They also turn their labellum face upwards, a movement called resupination, to best make it look like a bee or beetle resting on the plant. Once the insect is lured, the orchid's pollen sticks to it to be transferred to another orchid when the insect eventualy flies off to find another one that it mistakes for a mate. In Bulbophyllums, for instance, the lip is a sensitive hinge that swings to propel the visiting pollinating agent towards the pollen. In the Paphiopedilum orchid, or the Lady Slipper orchid, the lip has the shape of a pouch to trap the organism who will fullfil the pollination. In total, about one-third of the estimated 30,000 orchid species in the world rely on pollinator deception to get pollinated. The green-veined, or green-winged, orchid (Anacamptis morio), growing in W. Europe, a non-producing nectar plant, attracts the Queen Bumblebee, its main pollinator, by producing the same scent as the one in flowers producing large quantities of nectar; the insect, in search for the nectar, does the work without eventually getting paid for it. Of course, the pollinators are not stupid, they evolve to recognize the fraud, but the Orchids, respectively, continuously evolve their deceptive techniques to perfection; their survival depends on the outcome of this rally. We are talking here about a bunch of the best masters of deception in the Plant Kingdom!
It is high-time here we mentioned that Orchids can also self-pollinate, and they do in some circumstances. Self-pollination, though, is to be avoided as much as possible, because it results in offspring of worse genetic quality, a phenomenon called Inbreeding Depression. This is the reason for orchids to try and do their best to get help to achive cross-pollination.

2. The Orchid Column
The reproductive parts of the Orchids are unique. The male and female organs are fused into a sticky, tubular structure called the Column. In all other plants the sexual organs, male (the stamen with the pollen) and female (ovary with pistil and stigma) are separate, found either in the same individual (monoecious plants) or in male and female plants (dioecious plants). Monoecious plants have flowers that bear a gynoecium but no androecium (carpellate flowers on female plants) or flowers that have an androecium but lack a gynoecium (staminate flowers on male plants). In most (but not all) Orchidaceae androecium and gynoecium are fused together, so, they are, in a sense, monooecious plants. At the top of the column we see the pollinia, a number of roundish yellow pollen masses. The pollinia form the anther, which is covered by the anther cap. This is the male part of the flower.
On the underside of the column we see the female sex organ, the stigma. It is usually sticky, for the pollen dust to attach to it, but in Orchids it is so sticky that an orchid horticulturist suggested, jokingly, that the substance should be patented as it could prove financially profitable! (please see photo below: Head of a moth with its proboscis laden with seven pairs of pollinia from Orchis pyramidalis). When the pollinia get stuck on the stigma, one or more germinate to reach the ovary, part of the gynoecium, just under the column or more remotely, in the far end of an elongated spur. While most orchids bearing a spur have it going backwards and downwards, one genus (Anacamptis) have it extending upwards.
Some orchids, though, have distinct male, female and hermaphrodite flowers. For example, the orchid plant Catasetum had proved to be an unsolvable puzzle to the Linnaean Society. Charles Darwin  found that what had been thought to be three different genera of flowers growing on the same plant were actually the male, female and hermaphrodite forms of the flower of the orchid. This unusual plant, Darwin discovered, fired arrows with a sticky pollen head as the insects brushed past.
Last but not least, because pollination relying on deception can eventually fail, orchids are extremely prolific. Darwin himself had the patience of counting the number of Orchid seeds in various orchid species; he found them to be in the range of hundreds of thousands, to millions.  He concluded that their number exceeds the ability of the plant to supply each seed with adequate start-up germination nourishment. He suggested that seeds receive help by fungi, thriving on the latter's excrements. This inter-species cooperation gives orchids a tremendous advantage. He writes, zooming in Orchis maculata (New taxonomy:Dactylorhiza fuchsii):
"... Estimating in the same manner the smaller seeds of Orchis maculata, I found the number nearly the same, viz., 6200; and, as I have often seen above thirty capsules on the same plant, the total amount would be 186,300. As this Orchid is perennial, and cannot in most places be increasing in number, one seed alone of this large number yields a mature plant once in every few years. To give an idea what the above figures really mean, I will briefly show the possible rate of increase of O. maculata: an acre of land would hold 174,240 plants, each having a space of six inches square, and this would be just sufficient for their growth; so that, making the fair allowance of 400 bad seeds in each capsule, an acre would be thickly clothed by the progeny of a single plant. At the same rate of increase, the grandchildren would cover a space slightly exceeding the island of Anglesea; and the great grand-children of a single plant would nearly (in the ratio of 47 to 50) clothe with one uniform green carpet the entire surface of the land throughout the globe. But the number of seeds produced by one of our common British orchids is as nothing compared to that of some of the exotic kinds …  What checks the unlimited multiplication of the Orchideæ throughout the world is not known...”

3. The Orchid Root
Miraculous evolutionary solutions are to be observed also here. A great number of Orchidaceae species are epiphytic, i.e. growing on rocks or trees. Here roots have to undergo unique modifications, if they are to serve their water absorption duties. They are thick, otherwise, exposed to the air, they would dry out. They consist of an inner core with liquid transfer tubes, protected by a thick layer of dead cork-like cells, full of air cavities, called the velamen. It can absorb and store substancial amounts of water. This whole hydrating system is based on Capillarity: the capillary action is water movement against gravity, enhanced in trees by branching, evaporation at the leaves creating depressurization, and probably by osmotic pressure added at the roots and possibly at other locations inside the plant, especially when gathering humidity with air roots, as is the case here. This layer is further protected  by hair-like rootlets that both absorb humidity and keep the velamen wet. Additionally, they help provide the plant with energy, as they also contain photosynthetic plastids with chlorophyll (e.g.  Parish's Chiloschista, Chiloschistra parishii ). Non-epiphytic terrestrial orchids use their roots, besides their usual functions, as bulb-like storage organs, as in carrots and beets.

4. The Orchid long evolutionary history
In 2007, in a detailed study published in Nature magazine, a bee encased in amber, a fossil 10 to 15 million years old, was described to carry orchid pollinia stuck to its back. Researchers, though, believe Orchids to be far older, dating to perhaps 120 million years ago. They reached this conclusion having found two species of orchids genetically closely related in habitats thousands of miles apart. The only logical explanation is for them to have had a common ancestor before their habitats were separated by continental drift.

GENERAL FLOWER ANATOMY

A complete flower is defined as having sepals, petals, stamens and carpels, but all flowers contain at least one stamen or one carpel. However, the form of these anatomical parts varies widely between species.  Highly evolved flowers such as orchids have a complex pollination structure, whereas roses have a more typical flower structure.

To be able to describe our beloved flowers, we need to know the very special terminology. To the novice this may be an obstacle, mevertheless it is encouraging to know that it is a total of some thirty terms we are talking about.

 A drawing of the anatomy of a flower follows in the firste photo below.

Additional terminology is needed for the highly evolved orchids, which are the center of our interest in this album.

A drawing of the anatomy of an Orchid flower follows in the second photo below.