Each plant family has its own characteristics. Knowing a few of those will help in identifying each family and even the species. But, following the unique features of flowers of each family helps in zeroing the identity much easier. For example, Asteraceae with rings of sepals, petals, stamens and pistil in order; Convolvulaceae with a star pattern on its corolla; Liliaceae with all flower parts in multiples of threes.
In orchids, 3 sepals, 3 petals with one of them modified as lip, the unique column and the not so common presence of spur.
However, there are a few orchid species that defy the general rule – Corybas himalaicus (King & Pantl.) Schltr., is an example. Its flower is without any petals, and with 2 spurs.
The solitary flower of the plant is with unequal sepals – helmet shaped dorsal sepal, filiform (very narrow) shaped lateral ones, and a large lip.
The genus Corybas is also known as Helmet orchids due to its unique shaped dorsal sepal.
Corybas himalaicus (King & Pantl.) Schltr., is the only species in the genus Corybas found in India.
Terrestrial orchids are either rhizomatous or with tuber/s. Tubers play the role of food reserves and in many species new growths arise from it. Tubers are of different sizes and shapes. The surface of tubers are also unique, some are smooth but others are hairy, or even noded.
Tubers of many orchid species are collected because of their medicinal values.
The Ancient Romans used ground orchid tubers to make various drinks. Sahlep (or Salep) is a flour made from the tubers of orchid plants (in the genus Orchis) and considered highly nutritious and is consumed in beverages and desserts.
In general, inflorescence of orchid plants bear multiple flowers. Many species produce multiple inflorescences, thus with a large number of flowers. More the flowers, more the chances of getting pollinated and seed production.
However, there are many species that produce a solitary flower. In these cases, the plants have evolved to produce large and showy flowers or flowers with odour to attract pollinators.
It is to be believed that the family of Orchidaceae is the most evolved among all plant families. The life of many orchid plants is a mystery and many characteristics are still not yet fully studied.
One of those interesting characteristics is the flower opening patterns among various species. Flowers tend to open from the basal (bottom) toward the distal (apex) end in some species and vice versa in the others.
Flower characteristics are mainly to attract pollinators. Important and noticeable features include colouration of sepals and petals, position of the lip and odour (only in a few species).
However, many orchid species have evolved to great extent in having hidden or unnoticeable features (to human eyes) like colour patterns/spots on its anther cap and base of the lip to allure the pollinators deep inside the flowers to make effective pollination.
Almost all the orchid flowers are zygomorphic (bilaterally symmetrical), in simple meaning, a flower that can be divided into 2 equal parts by cutting through the middle.
In all the cases the sepals and petals are spreading or rarely arranged forward. However, in a few species the lateral sepals of the flowers are not spreading, but are joined and lying underneath the lip. Joined or fused sepals are termed synsepal.
Pseudobulb is an essential part of all sympodial orchids (a few exceptions are there with no pseudobulb). Leaf/leaves arise from the apex of the pseudobulbs; while inflorescence arises either from the apex or the base/side; bulb also store water to help the survival of the plant.
Pseudobulbs are of various shapes and sizes, from minute to stemlike. Its surface is also varying, from smooth to wrinkled or grooved.
The shape, size and surface of the pseudobulbs often help in identifying the species while not in flowers or leaf/leaves.
In a few orchid species, the peduncle and rachis get elongated after anthesis (flowering), while the fruits are developing. In many cases the combined length of the peduncle and rachis can achieve almost 4-5 times its length than while in flower.
Also, these species are conspicuous with their long maturing time of seeds, many take almost a year or so.
In an orchid flower, spur (if present) arises from the base of the lip and considered as an extension of the latter. Spurs can be very minute to shorter or longer than the length of the lip. However, in general, irrespective of its shape and size, lips are pendulous (pointing downwards), but in rare cases they are arranged backward pointing also.
However, as an extreme rarity some species have unusually large horn-shaped forward bending spurs.