REGIONAL DISTRIBUTION 505 



456. The eastern and central forest region. This region con- 

 tains more species of useful hard woods than any similar area 

 within the temperate zones. The oaks are the leading timber 

 trees, but others, as the hickory, the tulip tree, and the sassa- 

 fras, are of especial interest to botanists as characteristic Amer- 

 ican species. The northeasterly part of the forest region, while 

 it contains many hard-wood genera, such as beeches, elms, and 

 maples, is notable for its conifers. Chief among these are the 

 pines (Fig. 321), spruces, hemlocks, and white cedars (Thuja). 

 In the southerly part are several species of conifers, such as 

 bald cypress (Fig. 19) and long-leaf pine (Fig. 260), together 

 with such hard woods as walnuts, hickories, beeches, chest- 

 nuts, oaks, elms, magnolias, sycamores, and ashes. These are 

 deciduous mesophytes, but there are some water-loving trees, 

 such as the water hickory, the sweet bay, and the anise tree, 

 in the moister parts of the South, which may fairly be ranked 

 as hydrophytes. Some trees, as the bald cypress, may grow 

 either as hydrophytes or mesophytes. 



The forest region has always contained extensive treeless 

 areas. The earliest settlers found " openings " in the hard- 

 wood forests, and extensive prairies, marshes, and heaths, all 

 nearly or quite destitute of trees. Of course the tendency 

 under cultivation has been greatly to decrease the tree-cov- 

 ered area, and it is now very unusual to find bits of primeval 

 forest like those shown in Figs. 319 and 320. 



Since the forest region extends more than 1500 miles north 

 and south, it contains plants ranging all the way from sub- 

 arctic species, such as the dwarf herbaceous willow, saxifrages, 

 and crowberry, to sub-tropical ones, such as palms and ma- 

 hoganies. 



457. The Plains region. The prairies of the Middle West 

 merge imperceptibly into the Great Plains, which terminate, at 

 an elevation of 5000 feet or more, in the beginnings of the 

 Rocky Mountain system. The prairies of western Kansas, 

 western Iowa, Minnesota, Nebraska, and South Dakota have 

 less than 20 per cent of wooded surface, and the high plains 



