44 



SCIENTIFIC AGRICULTURE. 



a joint above the ground, which extend until they 

 reach and penetrate the soil. 



94. It was once supposed that roots have the 

 power of excretion, the reverse of absorption, but 

 Johnston says, " In the light of newer investigations 

 touching the structure of roots and their adaptation 

 to the medium which happens to invest them, we 

 may well doubt whether agricultural plants in the 

 healthy state excrete any solid or liquid matters from 

 their roots." The food that enters a plant through 

 the roots must be in a state of solution. There is 

 no doubt that plants have, to a certain extent, 

 the power of selection. We know that plants grown 

 on the same soil and under the same conditions do 

 not have the same elements in equal proportions. 



95. From the facts stated in reference to roots, 

 the importance of deep, thorough preparation of 

 land before planting, and of shallow cultivation after 

 the crop has been well started, is evident. Should 

 the soil, however, become hard and baked, it would ' 

 be good policy to cultivate deeply even at the risk 

 of destroying rootlets, which under such circum- 

 stances are necessarily sickly, that new and vigorous 

 ones may put forth and have mellow soil through 

 which to penetrate. No fixed rule can be laid down 

 to be rigidly followed in all cases. The intelligent 

 farmer or planter should be guided by the indica- 

 tions of the season, and the condition of his crop, in 

 the use of means necessary to meet an emergency. 

 Even the bird, though governed by instinct, modifies 



