CLASSIFICATION OF AxXGIOSPERMS. 245 



flowers. The perianth consists of six segments. The three outer 

 correspond to sepals and are similar. Two segments of the inner 

 circle correspond to petals and are alike, while the third, which 

 is known as the lip, is remarkably modified, being usually larger, 

 often spurred, and frequently reversed, being turned forwards 

 and downwards by the twisting or torsion of the ovary. Only 

 one of the stamens the anterior of the external whorl is devel- 

 oped and bears an anther. The other stamens are entirely want- 

 ing or present as staminodes (except in Cypripedium and the 

 Apostasiese). The filament is united with the style to form a 

 column, the so-called " stylar column " and the anther is thus 

 placed on its apex, and behind the stigma. The 3 carpels form 

 a unilocular ovary with 3 parietal, deeply bifid placentae. The 

 fruit (Fig. 256) is a capsule, which dehisces mostly by means of 

 6 valves, and contains numerous minute seeds, which are without 

 endosperm, and the embryo of which lacks frequently any trace 

 of external organs. The seed coat is membranous and loose. 



Vanilla planifolia, which yields the official vanilla, is a high- 

 climbing plant with long internodes and distinct nodes from which 

 arise more or less oval or broadly lanceolate, somewhat fleshy 

 leaves and also commonly a single aerial root. The long stem 

 is terminated by a raceme, flowers also arising in the axils of the 

 leaves for some distance back on the stem. The flowers are yel- 

 lowish-green and the segments of the perianth are similar, and 

 erect or spreading. The lip is united with the column, forming a 

 cylindrical body which is strongly concave on one side and spread- 

 ing at the upper portion. The pollinia are granular. Pol- 

 lination may be effected by insects but is usually brought about 

 by artificial means (hand-pollination). The fruits require several 

 months to become fully grown and an equal period of time is 

 necessary for their maturity which is indicated by their yellow 

 color. They are then gathered and cured by alternately steaming 

 and drying them when they acquire the dark brown color and the 

 odor of the commercial article. Vanilla is cultivated in all tropical 

 countries where the temperature does not fall below 18 C, and 

 the humidity is considerable. Usually vanilla culture is combined 

 with that of Cacao. The plants begin to yield fruits the third year 

 and continue bearing for thirt}- or forty years (p. 585). 



