DESCRIPTION OF THE COTTON PLANT 11 



water acids which aid in dissolving fresh supplies of plant- 

 food. While the root-hairs constitute the absorbing organs 

 of the plant, a small quantity of food in solution is absorbed 

 directly by the epidermal tissues of the true roots. The 

 process of absorption by both the root-hairs and the true 

 roots is that of osmosis.^ 



9. The stem. — The cotton plant possesses a cylindri- 

 cal, erect, gradually tapering central stem ranging in 

 length from two to six feet. From the nodes of this stem 

 the branches arise. The stem and branches are covered 

 with a tough greenish or reddish bark. Because of its 

 strength, due to the relatively large percentage of bast 

 fibers contained, cotton bark has been used to a limited 

 extent as a coarse fiber. Inside the bark the stem is com- 

 posed of brittle, white wood, which decays readily when 

 plowed into the soil. 



10. The branches. — Like all true branches, the 

 cotton branches arise in the axils of the leaves. As they 

 are borne at the nodes on the stem their number is deter- 

 mined by the length of the stems and the distance between 

 nodes. The Texas Station has found that late planting 



' "Osmosis. — When two solutions of different density are sep- 

 arated by a porous membrane, there will be first a movement of the 

 weaker sdution through the membrane into the stronger, and later 

 a return movement, the process continmng until the two solutions 

 have the same density. The contents of a ropt-hair being denser 

 than the soil solution surrounding it, there is a constant movement 

 of the soil solution into the root-hair. By some means the exosmosis, 

 which would take place in the case of an ordinary membrane (move- 

 ment of the cell solution outward), seems to be restrained in the 

 root-hair, probably by some functional activity of the cell. The 

 result is a much greater movement into the root-hair than exudation 

 out of it. The soil solution passes from the root-hair into the root 

 and is finally transmitted to the stem and leaves." — E. G. Mont- 

 gomery. 



