MESOPHYTES 



467 



have been found to transpire less than 3 per cent of their 

 maximum rate when leafy. 



Some of the principal differences between hydrophytes and 

 xerophytes may be summed up as follows : 



441. Mesophytes. A mesophyte is a plant which thrives 

 best with a moderate supply of water. The great majority of 

 the wild and the cultivated plants of the United States are 

 mesophytes. What has been learned from Part I of this book 

 about the forms, structure, and habits of ordinary plants, to- 

 gether with what the student's own observation, aside from the 

 study of botany, has taught him, should suffice to give him a 

 fair idea of mesophytic plant life. 



It is important to notice that most of our mesophytic trees 

 and shrubs pass the winter (or in the extreme Southwest the 

 dry season) in a leafless condition, and so transpire very little. 

 So, too, our mesophytic, herbaceous perennials, such plants as 

 the jack-in-the-pulpit, lilies, irises (Fig. 45), violets, and others, 

 lose a large portion of their evaporating surface during part of 

 the year by dying to the ground and leaving only the buried 

 bulbs, roots with buds at the crown, or rootstocks alive. 



All of the plants which make decided preparations for the 

 season when water is hard to get may be classed as tropophytes 

 or periodic xerophytes. 



442. Deciduousness an acquired habit. The practice of shed- 

 ding the leaves before the arrival of severe freezing weather, 

 when it becomes almost impossible to draw moisture from the 



