HORTICULTURAL SOCIETY OF NEW YORK. 



Structure and Classification of Orchids* 



By G. V. Nash, — January lo, 1906. 



What is an orchid? The general popular conception is that any plant 

 with curious flowers, or which has its habitat upon trees, should be referred 

 to this group of plants. The showy inflorescences, of many of the tail- 

 flowers, Anthurium, are popularly, though erroneously, called orchids. The 

 bromeliads, most of which occur on trees, are frequently regarded as 

 orchids. Perhaps the most curious mistake is to refer the East Indian 

 pitcher plant to this favorite lot of plants, and the error is often intensified 

 by calling the pitchers the flowers. 



It is rather difficult to give a popular description which will make it 

 easy to determine an orchid. A study of the flower structure, however, upon 

 which the botanist relies, will disclose the peculiarities which enable him to 

 at once tell them. A brief description of the flower, therefore, and of some 

 of the vegetative features of the plant, will not be out of place here. The 

 floral envelope, or perianth, consists of six parts, the outer series consisting 

 of three sepals, while the inner series embraces as many petals. The lateral 

 sepals are sometimes united into one organ, as is the case in the genus 

 Cypripedium, when there appear to be but two sepals. Of the petals, one 

 is usually highly modified and is called the lip. This assumes many shapes 

 from a small flat organ to a highly complicated one, such as is found in 

 Cypripedium and its allies, in Catasetum, and in Stanhopea. The ovary, as in 

 most of the mocotyledinous plants, to which the orchids belong, is usually 

 3-celled, or rarely i-celled, and is inferior. The stamens and pistils are 

 united into one organ called the column, and it is this feature which serves 

 at once to distinguish this family from all its allies. The stamens diflfer in 

 number. In one group, which includes Cypridepium and its allies, there are 

 two fertile stamens, and one sterile one, the latter known as the shield or 

 staminode. This group is known as the Diandrae. By far the greater num- 

 ber of orchids, however, have but a single stamen, and this group is hence 

 known as the Monandrae. The anther in this latter group is sometimes 

 attached to the column by a stout filament, it therefore remaining persistent. 

 In this group the pollinia (the masses of pollen grains) are usually granular, 

 and develops tails at the base. In the other group the filament is so fragile 

 that it breaks at the slightest touch, the anther hence readily falling and 

 usually carrying with it the pollinia, which, in this case, are waxy masses, 

 often translucent, and develop tails, if these are present, at the apex. The 

 stem is as highly modified as the flower. It is sometimes elongated, as in 

 the well-known genus Dendrobium, or it is as frequently as much shortened 

 and thickened, as in the genera Oncidium, Odontoglossum, and many of the 



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