lo MANURES FOR FRUIT TREES 



Root Absorption. — The roots of plants absorb 

 by osmosis water and mineral matter — tbe latter 

 in solution. Water acts upon the mineral ingredi- 

 ents of the soil, dissolving and disintegrating 

 them ; and the solvent power of water is greatly 

 increased by the presence of carbon dioxide origin- 

 ating in the soil through processes of decay. The 

 root-hairs are the organs by means of which the 

 absorption of water and mineral substances are 

 especially eflfected — they prepare food solutions 

 for trees and plants, which at once pass over into 

 the organism. 



The conditions relating to the absorption of 

 mineral substances by roots from nutritive solu- 

 tions are of a complex nature. The roots have a 

 selective action, as originally proved by De 

 Saussure.^ It is an interesting fact that the roots 

 of plants absorb solutions placed at their disposal 

 not necessarily in the form in which they are 

 supplied, but with a particular quantity of water 

 they take up, according to circumstances, some- 

 times smaller, sometimes a larger, quantity of 

 certain mineral matters. The root-hairs exude acid 

 excretions which corrode ^ the minerals of the soil. 



' De SausBure's book, loc. cit., p. 247. 



^ Sachs, Handbuch der Experimentalphysiologie der Pflanzen, 

 1865, p. 188. 



