22 Green Vegetable Manure. 



the Cobra de Capelho secretes the poison which is found 

 under its fang, from aliment which is not essentially different 

 from that employed by the most innocuous of the serpent 

 tribe ; and that fruit, which is sweet, palatable, and nutritious, 

 is the product of the same soil as the most bitter, nauseous, 

 and poisonous plants ? or that, in the same animal and plant, 

 secretions are found possessed of properties almost diametri- 

 cally opposite ? It is a fact, well known to physiologists, that 

 chyle, the substance produced by the change which the food 

 undergoes, before it mingles with the blood, has no analogy 

 with the character of the food from which it is formed, but 

 derives its peculiar properties from the action of the glands of 

 the mesentery by which it is prepared. Whether this be the 

 case with the sap of plants, which may be regarded as the 

 chyle of vegetables, we shall never, perhaps, be able to ascer- 

 tain, owing to the impossibility of obtaining it unmixed with 

 some of the ready formed secretions, previously deposited in 

 or near the root of the plant ; but, from the known characters of 

 sap, as it has been procured, we know that it varies much 

 less in different plants than we might a priori expect, on view- 

 ing the great diversity of their secretions. That it is not, 

 therefore, requisite for the vigorous growth of plants to ma- 

 nure the soil with fresh-vegetable matter, in order to enable 

 the plants to obtain their food in a state the least changed, and 

 decomposed by putrefaction, is obvious ; but it must, at the 

 same time, be admitted, that fresh-vegetable matter employed 

 as manure is admirably adapted to advance vegetation ; and 

 the following appears to me to be the true explanation of 

 this fact, and the cause of the great superiority of the crop, 

 on the portion of the field manured with the green Fern al- 

 luded to in Mr. Knight's experiment. 



One of the most striking, and the most universally known, 

 of the phenomena of the process of fermentation, is the extri- 

 cation of heat; and this principle, also, is the most powerful 

 and healthful stimulus of the vegetable excitability, when it is 

 not applied in excess. Now, the disposition of green or re- 

 cent vegetable matter to run into rapid fermentation is well 

 known; and it is easy to conceive, that matter of this de- 

 scription, placed under the soil so as to retain a considerable 

 degree of moisture, is in a situation the most favourable for 

 commencing and carrying on the process of fermentation ; 

 thence, the more recent the vegetable substance, the sooner 

 will the extrication of heat commence, and the longer will 

 it be given out. The surrounding soil, also, not being of 

 a combustible nature, and not a very good conductor of ca- 

 loric, the heat will spread in a more equable degree; while, 



