36 THE NATUBE AND WOBK OF PLANTS 



upright in a saucer of water an inch deep. Fill 

 the cavity with sugar. Examine five or six hours 

 later. The sugar will have drawn the soil water 

 from the saucer through the wall and filled up the 

 cavity perhaps to overflowing in a very close imita- 

 tion of the action of a root-hair. 



40. Action of root-hah^s on particles of mineral 

 substance. — The root-hairs take up the thin film of 

 water surrounding each particle of soil, and as the 

 walls of the hair are constantly satm^ated with acid 

 or other substances which will corrode rock, they 

 also dissolve some of it in such manner that it can 

 be absorbed. To demonstrate this action fill a small 

 flower-pot half full of common garden loam, and on 

 top of it lay a piece of marble, an oyster or clam 

 shell with a polished surface uppermost. Cover with 

 three inches of clean sand. Place one or two beans 

 in the sand, and water from day to day. After a 

 few days the seeds germinate and send down roots 

 through the soil, which come in contact with the 

 marble or the shells. Two weeks later remove the 

 marble or shell, wash clean, wipe, and allow to dry. 

 Hold between the eye and a window in such manner 

 that the surface will be seen by a reflected light. 



