CH. II.] THE ROOT. 65 



This increase of fragrance, if it be a truth, probably 

 arises from the same cause that ammonia increases 

 the pungent perfume of snuff. Flavours and scents, 

 we all know, are often made more intense by com- 

 bination. 



Plants are very much benefited by having oxygen 

 applied to their roots, being found to consume more 

 than their own volume of that gas in twenty-four 

 hours ; and when applied by Mr. Hill to the roots of 

 melons, hyacinths, &c., the first were found to be im- 

 proved in flavour, the second in beauty, and all in 

 vigour. Everything, therefore, that promotes the 

 presentation of oxygen to the roots of plants, must be 

 beneficial ; thus we find, that frequently stirring the 

 ground about them promotes their growth; for, in 

 proportion as the soil is loose can the atmosphere 

 more easily penetrate it. Moist earth rapidly ab- 

 sorbs oxygen from the atmosphere, as Humboldt has 

 demonstrated, but diy soil does not ; this affords an- 

 other reason for frequently stirring the earth about 

 plants during the di'oughts of summer ; for well pul- 

 verized soils admit the evening dews, more freely than 

 others more consolidated, and consequently dews will 

 be deposited more within their texture, and moisture 

 is more firmly retained in such pulverized soils, in as- 

 much as that they are not so much heated by the 

 sun's rays, being more pervaded by the air, which, 

 like all gases, is one of the worst conductors of heat. 



