164 LIVING PLANTvS 



proach of the inclement season. The leaves 

 of evergreens are so organized that the^^ tnay 

 Evergreen withstand the periods of drought or frost 



leaves through several years. Before such leaves 



enter upon a period of inactivity, alterations 

 are carried on in the cells, among which are 

 the reduction of the proportion of water pres- 

 ent, and chemical changes which result in the 

 formation of substances not affected by low 

 temperatures. The changes of color are not 

 so marked as to attract general attention, 

 and they are brought about by the withdrawal 

 of the chlorophyll bodies toward the inner 

 ends of the cells, and the formation of small 

 proportions of yellowish or reddish coloring 

 substances. The retention of the foliage is 

 made possible by adaptations in form and 

 structure, and is a result of the morphologi- 

 cal nature of the plants involved. 



