4S8 Ow the Food of Plants , 



must be conducted on or in the earth, we may consider these 

 operations as analogous to digestion : and just as the earth pos- 

 sesses the requisite qualities for digesting and distributing the 

 carbonaceous matter, or the food supplied, it will prove more 

 or less adapted to the support of vegetables. The digestive 

 powers of the earth must depend Upon its chemical qualities, 

 and its distributive powers on its mechanical texture. Thus, 

 Calcareous earths have great influence in modifying the de- 

 composition and recdmposition of animal and vegetable sub- 

 stances; and the mechanical texture of the soil, as it admits 

 ;iDr obstructs an equal and free distribution of water, must 

 also very much influence the growth of vegetables. 



Pursuing our comparisons, then; as we know that the health, 

 vigour, and prolificness of animals depend as much upon the 

 Quality and prdper digestion of their food as upon the quan- 

 tity, and upon the prdper adaptation of their lodging, and the 

 \;lirtiate which they are doomed to occupy, so we find it to be 

 me same with vegetables : and, as the success of the grazier 

 and breeder depends upon the skill with which the food is 

 selected and administered to his animals, the clean state of 

 *llieir lodgings, and the purity of the air in which they are 

 ^ept, so must that of the gardener with his plants. It is well 

 ^nowh, that if an animal which has been living on a poor and 

 meagre diet is suddenly supplied with an excess of highly 

 Simulating food, the dangerous disorder called a surfeit, and 

 all its consequences, will follow ; and such will always be 

 the case with vegetables : for whenever water containing a 

 iai'ge portioii of putrefying matter, frorn whatever source de- 

 i'ived, stagnates about the roots of a plant, it will produce 

 Wum, canker, morbid exudation, blotched and blistered leaves 

 'lihd shoots, fungus, &c. ; and a quantity of putrefying animal 

 matter being placed in contact with the roots of plants, and 

 ItoMing water in a stagnant state, will produce the same effects. 

 It is believed by some, that those diseases are merely local ; 

 fcciit this is a mistake. Local injuries may facilitate and deter- 

 '^line the appearance of disease ; but as the same kind of 

 'wound which will create inflammation, disease, and death, in 

 ;^ne animal, riiay be inflicted on anotTier without any such 

 Tnjurious Consequences, so it is with plants. A plant in a 

 %ealt*hy state may he wounded with impunity ; whereas the 

 'slightest bruise in one in an unhealthy state will immediately 

 putrefy, and produce a corrosive ulcer. But, whether these 

 comparisons be admitted as just or not, the causes and effects, 

 as explained, are found to be true, lay the practical demon- 

 strations of actual arid repeated experience and observation. 

 'If any petsdhs 'entertain iany doubt of the facts, let them 



