MESOPHYTES 



355 



In the Alleghany region and New England the upland 

 forests are very extensive and complicated, grading from 

 the rich flood-plain forests of the lower levels to the strictly 

 xerophytic forests (pines and black oaks) of the higher lev- 

 els, and dominated by various oaks, chestnuts, and hick- 

 ories. 



The flood-plain forests of New England are not so rich 

 as those of the Alleghany region and the central West, the 

 dominant forms being elm, 

 linden, ash, maple, syca- 

 more, tulip-tree, etc. 



215. Tropical forests. - 

 The forests of the rainy 

 tropics may be regarded as 

 the climax of the world's 

 vegetation (Fig. 319), for 

 the conditions favor con- 

 stant plant activity at the 

 highest possible pressure. 

 Such great forest growths 

 are found within the region 

 of the trade-winds, where 

 there is heavy rainfall, great 

 heat, and very rich soil, as 

 in the East Indies, and 

 along the Amazon and its 

 tributaries. So abundant 

 is the precipitation that the 

 air is often saturated and 

 the plants drip with the 

 moisture. 



The striking characteris- 

 tics of the great mixed trop- 

 ical forest are as follows: (1) There is no regular period for 

 the development or fall of leaves, and hence there is no time 



Fir,. 320. A gutter-pointed leaf of a rainy 

 tropical forest. After SCHIMPER. 



