CHAPTER III 



PHYSIOLOGY OF THE COTTON PLANT 



A PLANT, like an animal, is dependent upon certain vital 

 actions or functions to maintain life. Careful analysis 

 of a living plant shows it to be made up of distinct partg, 

 each part performing more or less definite functions. It 

 is essential, therefore, that we become familiar with the 

 more important of these functions and the relation of each 

 to the well-being^ of the plant. 



21. The plant structure. — The cotton plant is made 

 up of innumerable cells. Each cell in the hard part of 

 the plant has a somewhat thickened cell-wall, composed 

 chiefly of cellulose, the substance of which paper is made. 

 These cell-walls are united, the resulting tissue constitut- 

 ing the skeleton of the plant. There are tw;o kinds of 

 strengthening tissues composing the plant skeleton, differ- 

 ing mainly as regards the structure of the cell-wall. These 

 are (1) those tissues in which the cell-walls are thickened 

 at the corners only, (coUenchjona) and (2) tissues in which 

 the cell-walls are equally thickened throughout, (scler- 

 enchyma). The former tissue is found only in the young 

 growing parts of the plant, while the latter occurs in the 

 older parts in which growth has ceased. 



The function of the skeleton is to give stability to the 

 plant. It is by means of this strengthening tissue that a 

 cotton plant supports its own weight, and resists the force 

 of winds. 



22. The living substance in the plant. — Within the 

 cell-walls is contained a transparent, jelly-like substance 



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