64 



ELEMENTS OF AGRICULTURE 



for formation of chlorophyll, but it is no more necessary 

 than phosphorus and magnesium, and probably all the 

 other elements have to do with it either directly or indirectly. 

 A farmer interprets a light green color as indicating a 

 lack of nitrogen, not of iron. Plants that have an abun- 

 dance of manure, or nitrogenous fertilizers, are dark green, 

 while those that do not have enough nitrogen are light 

 green. An abundance of nitrogen promotes growth and 

 leanness in plants. Too much nitrogen makes oats gro^ 

 so rapidly that they are likely to fall down, hence, manure 

 or nitrogen, in fertilizers, is not often 

 applied on oats. A shortage of phos- 

 phorus and potassium is more likely to 

 show in poorly filled seeds than in lack 

 of vigor of growth. But we cannot sep- 

 arate out one particular element and say 

 that it has one specific function and that 

 one only. 



HOW THE PLANT GETS ITS FOOD - 



62. Root-Hairs. Germinate some oats 

 or clover seed as directed on page 51. 

 Examine the young roots for root-hairs. 

 The root is fairly covered with these 

 minute hairs, as in Fig. 38. These hairs 

 are not young roots. They are single- 

 celled tubes that absorb the soil solution. 

 Remove one of these seedlings, and see 



how easily these root-hairs are destroyed when handled. 



It would, of course, be very difficult to remove a plant 



FIG. 38. 



Root - hairs of a 

 radish. These absorb 

 most of the water 

 for the plant. 



