198 Plant Life and Evolution 



various ways. Some plants develop very many small 

 leaves, others a few very large ones, and the latter 

 may be entire as in the banana and many arums, 

 or it may be very much divided as in some of the 

 tree-ferns. Mesophytes predominate in the moister 

 temperate regions and in the shaded forests of the 

 tropics. With increasing moisture they approxi- 

 mate the hydrophytic type, and as the moisture de- 

 creases they assume more xerophytic characters. 



XEROPHYTES 



The term " xerophyte " has been applied to those 

 plants which exhibit more or less evident characters 

 adapting them to growth with a limited water 

 supply. As the amount of water is diminished in the 

 normally mesophytic plant, it becomes dwarfed and 

 the leaves are very much smaller, and at the same 

 time there is a thickening of the leaves, and often 

 greater hairiness. With the reduced leaf surface 

 there is naturally a correspondingly diminished 

 transpiration of water. 



Xerophytes Not Always Confined to Dry Re- 

 gions. While most mesophytes are able to adapt 

 themselves to a greater or less reduction in the water 

 supply, there are many plants which normally grow 

 in regions where they can receive only a very lim- 

 ited amount of water, and it is among these natural 

 xerophytes that the most remarkable adaptations 

 for economizing water are found. Xerophytes are 



