30 ANATOMY AND PHYSIOLOGY 



3. Distinguish the root- tip from the root-cap. Of 

 what is the latter composed? Describe it. Draw. 



C. The Function of Root-hairs: 



1. Carefully pull up a mustard seedling growing in 

 sand and having several leaves. Without injuring 

 the plant, carefully and very gently shake off all 

 sand that readily falls away. Does the sand adhere 

 with equal firmness to all portions of the root? 

 Describe in detail, explain, and illustrate by a 

 drawing, X2. 



2. Pull up another seedling of the same age, and remove 

 all or most of the adhering sand. Replant both 

 seedlings in sand, water them, and set them aside 

 until the next period. In order to eliminate indi- 

 vidual differences it is necessary to treat several 

 seedlings in each of the ways above indicated. 



3. At the next meeting of the class observe and com- 

 pare the appearance of the seedlings. In thor- 

 oughly removing the sand from the seedlings, how 

 were the root-hairs affected? 



4. By means of what organs does a land plant obtain 

 most of its water? State, in a paragraph, the 

 reasons for your answer. 



5. We have ascertained the organs whose function 

 it is to take in water from the soil. It is now 

 important to inquire by what process the soil- 

 water passes into the plant through the organs 

 of absorption. 



D. How the Root-hairs Take in Water; Osmosis: 



i. The preceding studies of the plant cell lead us to 

 recognize the fact that the root-hair is an individual, 

 elongated cell. Within is the cell-sap, a solution 

 of various salts ; without, as the plant grows in the 

 soil, is the soil- water, also containing numerous sub- 



