ECOLOGY 411 



Mesophytes. These are plants that grow in soil of an interme- 

 diate character which is neither specially acid, cold or saline, but is 

 sufficiently well supplied with water and rich in the elements re- 

 quired for plant growth. Plants which grow under such conditions 

 do not have structures by which transpiration is closely controlled. 

 They have large leaves frequently toothed and incised, with numer- 

 ous stomata usually on the lower surface and small intercellular -air- 

 spaces. The leaves and stems are usually of a fresh green color. 

 Typical of the mesophytes are the grasses and most of the annual 

 and biennial herbs of temperate regions. 



Tropophytes. This term was first introduced by Schimper in 

 1898 for land plants which have deciduous leaves and whose condi- 

 tions of life are, according to the season of the year, alternately those 

 of mesophytes and xerophy tes. The mesophy tic condition is found in 

 summer, when the trees, shrubs and perennial herbs, included in this 

 group, are in full leafage, and when, owing to the regular supply of 

 rain during the growing season, the soil is plentifully supplied with 

 water to meet the demands of -these plants during the period of active 

 transpiration. During the winter they are xerophytes. The 

 cold of winter freezes the water in the soil so that the transpiration 

 is reduced to a minimum, and this is associated with the fall of the 

 leaves of the trees and shrubs and the death of the overground parts 

 of the perennial herbs which spring up each year from their under- 

 ground parts. The vegetation of cold temperate regions is mainly 

 tropophytic. 



The deciduous trees and shrubs also known as the broad-leaved 

 plants and the summer-green plants form the principal tropophytes. 

 The deciduous forests, which include the oaks, the beeches, the 

 ashes, the maples, the walnuts, the chestnuts, cover a great part of 

 eastern and western China, central Europe (England, France, 

 Belgium, Germany) and eastern Australia, and are coincident 

 with the countries occupied by the most civilized races of man, such 

 as the Americans, Europeans, Chinese and Japanese. The cold 

 temperate climatic conditions which have determined the distribu- 

 tion of the forest trees have been influential also in the development 

 of the energetic races of mankind. 



