CLASSIFICATION OF ANGIOSPERMS. 501 



may be effected by insects, but is usually brought about by arti- 

 ficial 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, until 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 (Fig. 274). 



The yellow-flowering Cypripediums of the United States (C. 

 pari'iflorum and C. parviftorum pubesccns) yield the cypripedium 

 which was formerly official. The plants are a foot or two high. 

 The leaves are oval or elliptical (in the latter) or elliptical or 

 lanceolate (C. parviHorum) . In C. pubcsccns the lip is pale yellow 

 with purple veins, 25 to 50 millimeters long, and possesses a tuft of 

 white, jointed hairs at the throat. In C. parviflorum the lip is 

 smaller and non-hairy. C. acaule is shown in Fig. 275. 



The root-stocks of a number of Orchids are rich in mucilage 

 and yield the drug salep or a product resembling it. Salep occurs 

 in the form of globular or somewhat flattened, more or less trans- 

 lucent, light yellowish-brown tubers, 2 to 4 cm. long, of a horny 

 texture and a mucilaginous taste. The principal constituent is 

 mucilage, which originates in the cell-contents. It may contain 

 in addition either starch or sugar. 



While the Orchidaceae, which contains about 6,000 species, 

 ranks second in numbers to the Composite, there is probably no 

 family which exceeds it in interest. The plants are extensively 

 cultivated, and some of their flowers are the highest priced known 

 in the commercial world. There are few localities in which there 

 are not some orchids to be found, illustrations of several of which 

 are here shown (Figs. 275 to 279). 



B. CLASS DICOTYLEDONE^E. 



The following are some of the prominent features of the 

 Dicotyledons: (i) The leaves are reticulately (open) veined and 

 usually with an irregular margin, being sometimes deeply lobed ; 



