The Anatomy of an Orchid
Orchids possess an anatomy that is unique. Though there are over 20,000 natural species and possibly as many as 100,000 or more hybrids, they share many common characteristics. Those give the orchid its distinctive appearance.
Like animals species, flowers have male and female parts. The orchid is unusual in that its male and female aspects have been joined into one structure called a column. Surrounding that column are the 'orchid looking' sepals and petals. The column is about finger width.
Inside the column is the stigmatic surface containing the female organs of the plant, while the male organs comprise a structure called the pollinia. It's located under the anther cap.
The three sepals of an orchid resemble its petals. There are two lateral sepals and a dorsal sepal, with the latter often a little larger than the lateral ones.
The sepals are typically smaller than the petals but there is considerable variation from one species to the next. But even though they may look similar, they are the remains of a flower bud, and not a true petal. They tend to be very close to the same size within a given species.
The genuine petals of an orchid always number three, never more nor fewer. Two of these are flat to rounded, with a somewhat oval shape. The third is often enlarged, flatter and has a special structure. It's called the lip (or labellum, the Latin term). The enlarged platform gives a good resting place for pollinators that help ensure the survival of the species.
Those helpful creatures can range from insects like bees, butterflies and flies to ordinary birds or hummingbirds. Even some mammal species, such as bats, get into the act. They all feed on the nectar of the plant, getting pollen on their legs, wings and other body parts. They carry that pollen to other flowers, which then 'inseminates' the new plant.
In some cases the petals are very elongated, even to the point of becoming slightly twisted, as is Paphiopedilum parishii. There is also a considerable variation in size. Some petals, such as those of the Paphiopedilum sanderianum species, may reach lengths of 35 inches (90cm). Others are tiny as in the Oncidium. The lip may sometimes form a tube-shape and can have ridges and enclose nectar at the base. That tube is called a spur or angracecum.
The entire orchid is supported and fed by a stem and root structure that is very unlike those of most plants. Since orchids don't grow in soil - they cling to trees (epiphytes) or rocks (lithophytes), implant in leaf litter (saprophytes) or sometimes grow in sand (terrestrials) - their roots are fairly exposed. But they thrive by taking advantage of bird droppings as fertilizer, take water from drippings off leaves or tree bark, and employ other clever adaptation schemes.
