ORCHIDS OF JAMAICA 3 



rule, the most conspicuous feature of the flower, is often large and 

 spreading, or has upwardly curving sides. It is simple (undivided) 

 or two- three- or four-lobed and generally bears on the upper face 

 thickened veins or swellings (calli), or fleshy warts, which are 

 often, as in Oncidium, large and conspicuous. The lip is some- 

 times produced at the base into a sac or spur, which may arise 

 partly from the axis of the flower. 



The most characteristic feature of the flower is the develop- 

 ment of the receptacle, which at an early stage becomes 

 cup-shaped, and finally forms a hollow cylinder. The carpels 

 (three in number) arise as outgrowths from the edge of the cup, 

 on the interior of which the ovules are developed on three double 

 placental lines alternating with the carpellary outgrowths. The 

 perianth springs from the upper edge of the inferior ovary, 

 where there is often also an expansion of tjtie axis known as the 

 foot. The lateral sepals are continued along the sides of the 

 foot, from the tip of whiqh the lip springs at a sharp angle, 

 forming externally a chin, inside which at the base nectar is 

 often secreted. 



The stamens and stigmatic surfaces are raised above the 

 perianth on an elongation of the floral axis known as the 

 column; occasionally some of the other organs are raised up 

 on the column, as in Ponthieva, where the petals and lip are 

 carried up above the sepals. Comparative study of tt^e orchid 

 flowers among themselves, and especially with those of ot^her 

 families of Monocotyledons, suggests that the stamens are derived 

 from two alternating whorls, each of three members, the members 

 of the outer whorl alternating with the petals. The stamens are, 

 however, much reduced, and are represented in the great majority 

 of orchids by one anther, which is variously placed on or near 

 the apex of the column, and represents the median stamen of 

 the outer whorl, opposite the median sepal. There is generally 

 no trace of the other members of this whorl, but they sometimes 

 appear as small outgrowths on the side of the column ; and the 

 lateral pair of the inner whorl is also often similarly represented ; 

 in Epidendrum Ottonis they are more or less fertile. The presence 

 of a single fertile stamen characterises the great majority of the 

 genera ; in the genus Cypripedium, not found in Jamaica, the 

 lateral stamens of the inner whorl are fertile, while the median 

 stamen of the outer whorl is represented by a large staminode. 



Cypripedium has three functional stigmas ; but in Jamaican 

 orchids only the lateral pair are functional, the third is 

 sterile and forms the rostellum, which often plays an important 

 part in transference of the pollen. The stigmas form a smooth, 

 viscid, flat or cushion-like are^, on the inner face, or sometimes on 

 the end of the column, or two distinct processes whiph in 

 Sahenaria are borne on projecting style-like structures. 



B 2 



