550 A TEXTBOOK OF BOTANY [Ch. XIII 



sweet. Most prominent are the Maples, verj' valuable trees, 

 most of which have returned to wind pollination and dis- 

 semination, though the allied Horse Chestnut and Buckeye 

 keep the showy flowers. Allied is the Balsam family, includ- 

 ing the familiar garden herbs, with the wild Touch-me-not. 



Order 19. Rhamnales: the Buckthorns and Grapes. 

 About 1000 species of trees and climbing shrubs. The 

 Buckthorn family is not prominent, but in the Vitacece are 

 included the Grapes (Vitis), with their reduced but insect- 

 pollinated flowers, and their familiar fine valuable fruits. 

 Here also belong the Virginia Creeper, and Japanese Ivy. 



Order 20. Malvales: the Mallows and kin. About 

 2100 species of herbs, shrubs, and tropical trees, related to 

 Sapindales. Here belong the Lindens, or Basswoods, valu- 

 able trees : the true Mallows, with showy flowers, familiar in 

 Hollyhock and Marsh Mallow, and the Cotton Plant (Gos- 

 sypium herbaceum), of which the seeds yield the invaluable 

 fibers (Fig. 254) and a valuable oil. With this group belongs 

 also Theobroma Cacao, the small tree which yields Cocoa and 

 Chocolate. 



Order 21. Parietales. About 3000 species, mostly 

 tropical, of trees and shrubs, related to Rosales in many 

 features, but distinguished by the parietal placentae, whence 

 their name. They are known to us chiefly through the Tea 

 (Thea) and the Camellia, which are closely related, the Vio- 

 lets, the Passion Vines (Passiflora), and the Begonias, cul- 

 tivated for the diversity of their foliage. Here also belong 

 the Papaya, a, well-known sub-tropical fruit, and the Tama- 

 risk, a graceful garden shrub. 



Order 22. Opuntiales: the Cacti. A homogeneous 

 group, some 1200 species, of well-known desert succulents 

 (Fig. 396) almost wholly American, though a few now run 

 wild in Europe. They have large and beautiful flowers, 

 with inferior ovary and many parts. They show a com- 



