of the Hotation of Crops. 1 7 



pot, and with it a single strawberry plant, without any manuring 

 substance. The soil, in the first instance, shall be of an ochreous 

 yellow hazel colour. In a single year, how many shades, ap- 

 proaching to black, will it acquire from the deposition of carbonous 

 matter, although it be watered with pure rain water only ? Let 

 experimenters determine this and other facts of the like nature, 

 for their own satisfaction : I throw out the hint as a stimulus. 

 It must be conceded, that great difficulty surrounds experiments 

 of a nature similar to those instituted by M. Macaire; for 

 plants in water are not in a purely natural situation : they live, 

 and perhaps grow ; but they are not, as the plants in the field, 

 rooted and established in soil, and exposed to the stimulus of the 

 great natural agents. Hence, there is great danger of being 

 deluded by appearances. A cutting, placed in a coloured in- 

 fusion imbibes the colouring matter, and has induced microscopic 

 observers to suppose that they have thereby detected the genuine 

 channels of the sap : but, as I have shown [VIII. ] 42.], rooted 

 plants do not evince the same appearances of colour, although 

 the soil in which they have grown has been moistened for a long 

 time with deeply coloured infusion. Plants, in a word, elaborate 

 their own food ; they are their own chemists, and ought to be 

 placed in their peculiar spheres of action ; otherwise, though life 

 may be protracted, their functions are not naturally performed, 

 nor are their secretions regularly and healthily effected. 



The writer in the Quarterly Journal of Agriculture invites che- 

 mists to investigate and experimentise, in order to improve upon 

 and establish, or to disprove, the theory of Professor de Can- 

 dolle. I, for one, would volunteer my services, the more espe- 

 pecially to consolidate my own hypothesis; but I must, in justice, 

 caution every one, that, in order to determine the causes of 

 natural phenomena, the subjects of trial must be placed in truly 

 natural situations. Cuttings afford fallacious data. I am inclined 

 to fear that even rooted plants, growing in pure water only, would 

 not yield products exactly corresponding with those afforded to 

 the soil. In order to operate efficiently, I conceive it would be 

 prudent to wash a sufficient bulk of maiden earth in rain water, 

 to drain it thoroughly, then to plant the subject in a pot of the 

 washed earth, and to water it during its growth solely with fil- 

 trated rain water. Plants so treated, and duly exposed to sun 

 and air, might be expected to yield their specific radical exudation 

 to the soil. After a given time, the mould should either be 

 repeatedly watered to excess, and the drainage collected for 

 experiment, or, the plant being removed, the whole bulk of soil 

 should be immersed in rain water, and stirred over and over 

 again. After three or four hours, the water might be filtrated 

 through strong bibulous white paper, and tested according to art. 

 These crude hints are thrown out, leaving the minutia? to the 



Vol. X. — No, 48. 



