36 



Plant Physiology 



concerned with the use and distribution of water and of 

 substances in solution. 



Properly to consider the use of water there arises the 

 necessity of learning or reviewing the structure of the 

 organs and the nature of the processes whereby water is 

 absorbed, conducted, and eliminated, as well as general 



FIG. 7. 



Thrifty squash-plants as typical examples of the relation of 

 water-content to rigidity. 



and special crop relations in which this factor plays an 

 important role. 



25. Hydrostatic rigidity. Under conditions favorable 

 for growth, it is obvious that the living cells of a plant are 

 commonly in a state of extension or hydrostatic rigidity. 

 Small and succulent stems are able under such circum- 



