232 CONSERVATIVE ORGANS. [LECT. V. 



matter then the carbon is supplied ; and as water 

 only, and those substances which it can hold 

 in solution, can be absorbed by the mouths of 

 the roots of plants, the carbon which is con- 

 tained in the soil, separated from vegetable and 

 animal matters by decomposition, must be dis- 

 solved in the water in order to be taken into the 

 system of the plant * ; and it thus becomes their 

 proper food. 



If this view of the subject be correct, the art 

 of the husbandman and horticulturist must con- 

 sist in applying those substances to the soil which 

 will promote the growth of plants without over- 

 stimulating them. The different matters known 

 under the title of manures, which are employed 

 for this purpose, must act in four ways to pro- 

 duce the effect required. 1. They must render 

 the soil of that consistence which will enable it to 

 retain a sufficiency of water; but not too much. 

 2. They must render it pulverulent to admit the 

 roots of the plants to permeate, and spread freely 

 in it. 3. They must enable it to admit and retain 

 air in its interstices : and, 4. fit it to form carbon, 

 and afford healthy stimuli to the vegetable irrita- 

 bility. The importance of a finely pulverized 



* The pores in the fibrils of plants are so minute, that a pow- 

 erful microscope is required to discover them ; the extreme 

 division, therefore, of insoluble matters, which pass into the 

 vegetable system may readily be conceived. 



