CHAPTER IT 



PLANT PHYSIOLOGY AS RELATED TO 

 PRUNING 



4. Plant cells and their functions. — Knowledge of the 

 "living machinery" upon which fruit and ornamental 

 plant growers depend for profit or beauty depends pri- 

 marily upon knowledge of the minute structure and the 

 functions of plant cells. It is not necessary in the present 

 discussion, however, to go into the 

 matter as deeply as does the plant 

 physiologist, even though in prac- 

 tically all physiological processes 

 plant cells form "the important sub- 

 stratum of all vital activity." 



5. Cell. — "One of the structural 

 elements of living bodies, by which 

 the multiplication of growth is 

 affected. In plants the cell usually 

 appears as a closed sac surrounded 

 by a firm wall of cellulose and con- 

 taining the essential element, proto- 

 plasm, and usually a nucleus, the active agent in cell- 

 division" (Crozier). 



6. Protoplasm. — "The viscid, contractile, semi-liquid, 

 more or less granular substance that forms the principal 

 7)ortion of an animal or vegetable cell" (Standard Dic- 

 tionary). "The physical basis of life" (Huxley). 



7. The water supply has much to do with the activities 

 of protoplasm and cells and the organisms which these 

 compose. Unquestionably it more definitely sets the 

 bounds of plant growth as to habitats, localities and re- 

 gions than does any other environmental, physical factor; 

 for, unless the plant can secure a sufficient and practically 



G 



FIG. 5 

 MERISTEMATIC CELL 

 FROM ROOT TIP OF 

 MAIZE 



