64 



THE PLANT 



necessary for the plant. The cells in all parts of the plant are 

 nourished by this leaf-formed food and there are two currents to 



carry it. One goes up 

 from the roots through the 

 soft sapwood to the leaves, 

 and the other passes down 

 through the bark with 

 nourishment to the roots. 

 In the center of a tree 

 there is little or no sap 

 movement, and hence all 

 growth ceases there. If 

 we girdle a tree, the down- 

 ward movement of the sap 

 is arrested, and no nourish- 

 ment is carried to the 

 roots. In a little while 

 they cease to grow and fail 



Diagram of the formation of starch. to take in water in guffi _ 



cient amounts for the needs of the plant. As a result, the leaves 

 wither and after a short time the plant dies. In transplanting 

 trees we usually break and injure many of 

 the roots so that an insufficient amount of 

 water is absorbed and the leaves wilt and 

 wither away. 



If we sprout some oats in a germinator 

 and examine them closely a few days later, 

 we find many delicate hairlike appendages 

 studding the surface of the larger roots. 

 These small growths are called root hairs, 

 and they are of great value to the plant. 

 In some plants we often find as many as 

 forty thousand of them on a single square 

 inch. It is through these that the moisture 

 of the soil is absorbed for the use of the 

 plant instead of through the thick heavy 

 roots. The activity of these root hairs 

 or rootlets may be appreciated when we Roots of oat plant. 



