166 AMERICAN HUSBANDRY. 



root itself, deprived of its more dense covering or 

 cuticle, as it is termed. This opinion is very much 

 strengthened by the well-established fact, that roots 

 grow by their extremities only, in this manner the 

 spongiole is always being renewed ; and, what is of 

 still more consequence, is never long in one place. 

 On ihis account it is that plants which live many 

 years (if not growing too near othera of the same 

 kind) are not liable to die from having exhausted the 

 soil ; or, in other words, are not liable to be starved 

 to death ; for it is evident that, by the constant 

 change of position of the spongiole, which is the only 

 part of the root by which nourishment is received 

 into the plant, there must be a constant supply of 

 food, so long as the soil around it contains any or- 

 ganic matter in a jit state for absorption. It has 

 been shown, by innumerable experiments, that the 

 spongioles, or absorbent extremities of the roots, 

 cannot take up anything but fluids ; or, at all events, 

 if they can absorb solids, they must be in such a 

 minute state of division that they would remain sus- 

 pended in water even for a considerable time, which 

 is a fineness of particles far greater than will proba- 

 bly ever be attained by any mechanical means. 



It has likewise been proved that plants are capa- 

 ble of choosing, to a certain degree, their food ; or, in 

 other words, of selecting those substances which 

 are best adapted for their peculiar nature, and re- 

 jecting what would be injurious. This power, how- 

 ever, appears to be limited, as it is perfectly possible 

 to destroy a 'plant by giving it poison by the roots. 

 The root, moreover, has the power of excretion, or 

 returning to the earth such matters as are either 

 useless or injurious. From this last property of 

 roots, we may draw two valuable conclusions : first, 

 that, in order to poison a plant, the substance used 

 must be capable of acting rapidly, or it will most 

 probably be rejected before it has had time to pro- 

 duce its effect ; and, secondly, that, since plants reject 



