HELPING PLANTS GROW 



a 6 . 



squash plants would extend fifteen miles. The tendency of 

 a root-system to reach into all parts of the soil near its surface 

 is an important fact to remember. Thus, when the soil 

 between rows of plants, like corn, is cultivated deeply, es- 

 pecially late in the growing season, many 

 feet of small roots will be destroyed. 



Root-systems are of two kinds; those 

 having a central root with smaller roots 

 radiating from it, and those having a 

 number of roots of nearly uniform size 

 extending from the part of the plant lying 

 just beneath the surface of the soil. The 

 former is called tap-root and is illustrated 

 by the roots of such plants as the com- 

 mon clover; the latter are fibrous roots, 

 illustrated by roots of such plants as com- 

 mon grasses. Tap-rooted plants are as a 

 rule deeper growing than those having 

 fibrous roots. This fact is sometimes of 

 practical value in selecting a crop for 

 very shallow soils, or for a rotation be- 

 tween shallow and deep-rooted plants. 



How root-hairs take water from the 

 soil. Root-hairs have been referred to 

 as the absorbing organs of the root. 

 The way in which these hairs are able to 

 absorb water from the soil may be illustrated by a simple 

 experiment. If a bladder with a glass tube securely fastened 

 into its neck is filled with a solution of sugar and then im- 

 mersed in water with the tube above, the solution will begin in 

 a short time to rise in the tube. This action is known as 

 osmosis. It always takes place when two liquids of different 



Diagram of simple 

 apparatus for demon- 

 strating osmosis. 



A. Tube. 



B. Sugar solution 

 within tube. 



C. Water 



D. Membrane 

 lima bean skin sepa- 

 rating sugar solution 

 from water. 



E. Cardboard sup- 

 port for tube. 



