THE ROOTS 35 



the soil water is drawn through the walls into the 

 cavity in the same manner as through the parch- 

 ment. Besides this attractive power of the solution 

 inside the root-hair, the thin layer of living matter 

 lining the wall is of such nature that it attracts 

 water, and it will allow the passage of soil water 

 containing mineral substances ; but will not permit 

 the escape of any of the liquid containing sugar, 

 except in the most minute quantities. The small 

 amount of acid which does escape is seen to act 

 very strongly on the rocks in the soil (§ 40). 



38. Action of sugar. — The manner in which 

 sugar draws water into the root-hair is illustrated 

 by the following method : Cut away the top of a 

 carrot, and dig out a cavity as large as an acorn. 

 Fill the cavity with dry sugar and set aside for a 

 few hours. The sugar will be converted into sirup, 

 having drawn water through the walls of the cells 

 of the carrot. 



39. Another method of imitation of the action of 

 root-hairs. — Select a long, sound potato, and bore 

 a cavity in it reaching from one end nearly to the 

 other, being careful not to split it. Trim the skin 

 from the closed end and shape it so that it will stand 



