TREES, SHRUBS, AND FORESTS 



381 



oaks, poplars, hickories, ash, willows, and other well-known 

 species of broad-leaved trees. This hardwood forest of the central 

 region differs from that of the coniferous forests in that it is not 

 so continuous, being composed of smaller local forest stands or 

 of groups of trees on farms, known as the farm wood lot. 



Reproduction. The hard woods belong to the angiosperms, or 

 true flowering plants, and are hence sharply distinguished from 

 the cone-bearing gymnosperms. 

 The flowers of the fruit bearers, 

 such as the apples and plums, 

 have already been discussed and 

 are familiar features of these 

 trees in the spring on account of 

 their great beauty and fragrance. 

 Many of the shade and timber 

 trees, however, reproduce by 

 means of very simple flowers 

 which are rarely known to any- 

 one except the student of botany. 

 In some cases, as in the oaks 

 (Fig. 238), these simple flowers 

 are thought by many botanists 

 to indicate a very early ancestry, 

 even antedating that of herba- 

 ceous species, while others regard 

 the simplicity of the flowers as 

 indicative of a reduced condition. In most of these cases polli- 

 nation is anemophilous (by the wind) and the trees are either 

 monoecious or dioecious. 



Many trees produce winged fruits, which greatly facilitate 

 their dissemination, as in the poplars, which so frequently re- 

 forest burned-over areas on mountain slopes. Other species, like 

 the oaks and hickories, produce heavier nut fruits, which are 

 not easily distributed and hence limit the range of these species. 



Commercial importance. The commercial importance of the 

 hardwood trees is determined by the character of the fruit and 

 the wood. In the wild state the wood is the most important 



FIG. 234. Transverse section of the 

 wood of sassafras, showing its ring- 

 porous character 



Photomicrograph by R. B. Hough 



