CHAPTER XX 



HERBACEOUS AND WOODY DICOTYLEDONS 



The dicotyledons are the largest and probably the oldest 

 group of true flowering plants ; the monocotyledons are supposed 

 to have originated from them in late geologic times. The dicoty- 

 ledons comprise over a hundred thousand known species, ranging 

 from trees and shrubs to the simplest types of herbaceous plants. 

 They are also adapted to the most diverse conditions of soil and 

 climate, being widely disseminated o^er all parts of the earth as 

 mesophytes, hydrophytes, and xerophytes. Their chief distinctive 

 characteristics are their broad, net-veined leaves, the active cam- 

 bium of the stem, the floral plan, and the two cotyledons of the 

 embryo which give to the group the name dicotyledons. 



The following representative families and species are discussed 

 in order to furnish an introduction to the biological and economic 

 aspects of the group. 



RANUNCULACEAE (BUTTERCUP FAMILY) 



The Ranunculaceae include many of our commonest and most 

 typical plants of the spring flora. Among these the buttercups, the 

 marsh marigold, the hepaticas, and the wood anemones are early 

 harbingers of spring, which represent at the same time the simpler 

 types of plants in the family, with regular spiral and hypogynous 

 flowers. Among the more highly modified and showy flowers of 

 the family the columbines, larkspurs, and clematis represent both 

 wild and cultivated species of great beauty and usefulness as 

 ornamental plants. Most of the species are stemless herbs with 

 simple leaves, which produce their flowers and fruits early 

 in the spring. 



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