THE CLASS DICECIA. 



171 



Betula yields a fermenting juice, from which a good wine is produced (page 23) ; and 

 the Pinus affords turpentine and resins ; but it is the wood which this class yields that 

 contributes to its value, 



CLASS XXII. DICECIA. 



This agrees with the former in all the flowers being unisexual, and having either 

 stamens or pistils alone ; but it differs in this respect, that the two sexes occupy different 

 trees. Thus one plant has wholly male flowers, and another has exclusively female 



Fig. 369. Dicecia Triandria. Fig. 370. Dioecia Icosandria. Fig. 371. Dioecia Enneandria. 



ones. It contains fourteen genera and eighty-two species, divided into twelve orders, 

 viz,, Monandria, Diandria^ Triandria, Teirandria, Pentandria, Hexandria, Octandria, 

 Enneandria, Decandria, Icosandria, Polyandria, and Monodelphia. This extreme 

 division of its contents clearly proves that it possesses very heterogeneous materials. 



Fig. 372. Dioecia Octandria. Fig. 373. Dioecia Pentandria. Fig. 374. Dioscia Hexandria. 



The order Diandria is occupied by the genus Salix a genus which affords sixty- four of 

 the eighty-two species of the class. It is known by the catkin inflorescence described 

 at page 106. Triandria and Tetrandria have three genera each ; and of these only one 



j Fig. 375. Dioecia Diandria. Fig. 376. Dicecia Monandria. Fig. 377. Dioecia Dodecandria. 



I of the latter, Viscum Album, or Mistletoe, deserves mention. The valuable and scarce 



| Humulus, or Hop, occupies the outer Pentandria ; and Tamus, or Black Bryony, the order 



Hexandria. Populus, or the Poplar-tree, is found in Octandria ; and Mercurialis and 



