CLASSIFICATION OF ANGIOSPERMS. 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 sometimes inferior (below the ovary) by the 

 torsion of the ovary or stalk of the flower. The stamens are 

 variously united with the style, forming an unsymmetrical col- 

 umn. The anther is 4-locular and does not dehisce at maturity. 

 The pollen grains form from two to eight club-shaped masses 

 (pollinia) which are withdrawn by visiting insects and carried 

 to other flowers. The viscid stigma either faces the lip of the 

 corolla or is embedded between the pollen sacs. The seeds are 

 very numerous, exceedingly small and without endosperm. 



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 a single aerial root (Fig. 133). 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 top (Fig. 133, A). The pollinia are granular. Pol- 

 lination may be eff^ected 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 thirty or forty years (p. 585). 



The yellow-flowering Cypripediums of the United States 

 (Cypripedium hirsiitum and C. parviHorum) yield the cypripe- 

 dium of the Pharmacopoeia (p. 490). The plants are a foot or 

 two high. The leaves are oval or elliptical (C hirsutum) or 



