Seed Plants : Angiosperms 



305 



FIG. 178. A deciduous forest In Illinois. The trees are oak, hickory, and elm, 

 important and typical dicot trees. 



exception of the palms, bamboos, and a few other species, the 

 Monocotyledons are herbs ; and the tissues of even the woody 

 Monocotyledons are generally less woody than are those of 

 the conifers and the dicotyledonous trees and shrubs. This 

 great assemblage of flowering plants includes not fewer than 

 25,000 species. 



Dicotyledons. The floral parts of Dicotyledons are usually 

 in groups of five or four ; the vascular bundles are arranged 

 in a circle about a central pith ; the bundles are open, which 

 makes possible an increase in stem diameter and permits forms 

 like the trees to reach a great size ; the leaves, with few 

 exceptions, are net-veined ; and the embryo has two coty- 

 ledons. In size the Dicotyledons range from the smallest 

 herbs to the largest of our hardwood trees. 



