CLASSIFICATION OF ANGIOSPERMS. 341 



ical America, the best known of which is the genus Carica. The 

 Papaw or Melon tree {Carica Papaya) is a small tree with a 

 straight, slender, usually unbranched trunk which bears at the 

 summit a cluster of long-petiolate, deeply-lobed leaves. The 

 flowers are dioecious, and the fruit is a large, melon-like berry. 

 The green fruits as well as the leaves contain a milk- juice which 

 is obtained by incising them. The material is dried and is used 

 in medicine on account of its containing a proteolytic ferment, 

 papain or papayotin, which is active in the presence of both acids 

 and alkalies. The leaves and fruit also contain the alkaloid car- 

 paine, and in addition the leaves contain the glucoside carposid. 

 The root contains a glucoside somewhat resembling potassium 

 myronate and a ferment which has a decomposing action upon it. 

 A proteolytic ferment is also present in the leaves of Carica quer- 

 cifolia of Argentina. The melon tree is cultivated on account of 

 the fruits, which are edible. 



o. BEGONIACE^. This is a family of tropical plants which 

 are extensively cultivated. They are herbs or shrubs frequently 

 with tuberous rhizomes and with characteristic, asymmetric, varie- 

 gated leaves. They are easily propagated by cuttings providing 

 they have sufficient moisture, even the leaves giving rise to new 

 plants. The roots of Begonia anemonoides of South America and 

 B. gracilis of Mexico contain purgative principles. Calcium oxal- 

 ate and acid oxalates are found in the leaves of probably all of the 

 species of Begonia. The roots of a number of species of this 

 genus are astringent. 



p. DATISCACE^. The plants are trees or shrubs found 

 principally in the Tropics. A bitter principle is found in the Yel- 

 low hemp {Datisca cannabina) of Southern Europe and the 

 Orient. The root contains a yellow coloring principle, datiscin, 

 which is used in the dyeing of silk. The wood of Octomeles and 

 Teframeles is used in the making of tea-chests. 



XXI. ORDER OPUNTIALES. 



The plants of this order are succulent, with much reduced 

 leaves, and with flowers characterized by having a perianth with 

 numerous segments and an inferior ovary. 



