??ATURE AND PROPERTIES OP THE SOIL. 05 



manner, it should be considered, that whatever may be the 

 nature of the substances derived from manure, they cannot 

 communicate nourishment to the plant, without first going into 

 a state of solution ; and that water is the agent made use of to 

 effect this solution. For as water has been proved by various 

 experiments to be insufficient, of itself, to bring the seeds o^ 

 any plant to maturity, while at the same time the presence of it 

 is indispensable to carry on the process of vegetation, we are 

 forced to conclude, that the principal, if not the sole use of it, is 

 to dissolve all those substances which form essential parts of 

 the food necessary to its growth and maturity ; especially, 

 since it has been well demonstrated by experiments, that all 

 those substances may be dissolved in water. So far, then, as 

 the food of plants is supplied by the soil in which they vege- 

 tate, it is probable that it is imbibed by the extremities of the 

 roots only. For it has been discovered, that the portion of the 

 soil which is soonest exhausted, is precisely that part in v/hich 

 the greatest number of the extremities of roots lie. By this- 

 means it has been observed, they are enabled to go in quest of 

 nourishment, and the extremities of the roots seem to have a 

 peculiar structure, adapted for the imbibing of moisture : al- 

 though it has no visible opening, yet, if we cut it off, it never 

 increases any more in length, and its use, as a root, is in a 

 great measure destroyed ; but its sides send out fibres which 

 act the part of roots, and imbibe food by their extremities. 

 This is the theory in which chemists are generally agreed, 

 respecting the manner in which food is communicated to the 

 plant, so far as it is supplied from the soil. Plants derive some 

 part of their nourishment from the atmosphere. The house- 

 leek, and some other plants, may be supported from the influ- 

 ences of the atmosphere alone. But the influence of the at- 

 mosphere on the vegetation of plants generally, is efficacious, 

 in proportion to the productive power of the soil, or the efficacy 

 derived from its fertility. From what has been observed, it 

 will be seen that the nourishment derived from manure, must 

 first be dissolved by the moisture there is in the soil, and 

 after being so dissolved, must come in contact with the ex- 

 tremity of the roots of tJie plant, before it can contribute to its 

 growth and maturity. It is not known that there is any attrac- 

 tive power, either in this i.carishment, or in the roots of the 

 plants, by means of which the former is communicated, so as to 

 promote vegetation. It i ^ obvious the plant will not flourish, 

 unless some such nourishment may be found located in those 

 parts of the soil to which the extremities of the roots will, in 

 tlie progress of vegetation, become contiguous, or nearly so. 



