LECTURE IX. 



Inorganic constituents of vegetable substances. — Relative proportions of organic and Inor- 

 ganic matter in plants. — Unlike proportions in unlike species. — Kind of inorganic matter 

 whicii exists in different species.— Nature and properties of the several inorganic elemera 

 tary bodies found in plants. 



* The consideration of the inorganic constituents of plants is no less 

 important to the art of culture than the study of their organic elements, 

 which has engaged our sole attention in the preceding part of these lec- 

 tures. 



It has already been shown that when vegetable substances are heated 

 to redness in the air, the whole of the so-called organic elements — car- 

 bon, hydrogen, oxygen, and nitrogen — are burned away and disappear ; 

 while there remains behind a fixed portion, commonly called the ash, 

 which does not burn, and which in most cases undergoes no diminution 

 when exposed to a red heat. This ash constitutes the inorganic portion 

 of plants. 



The organic or combustible part of plants constitutes, in general, 

 from 88 to 99 per cent, of their whole weight, even after they are dried. 

 Hence the quantity of ash left by vegetable substances in the green 

 state is often exceedingly small. It therefore long appeared to many, 

 that the inorganic matter could be of no essential or vital consequence 

 to the plant — that being, without doubt, derived from the soil, it was 

 only accidentally present, — and that it might or might not be contained 

 in the juices and solid parts of the living vegetable, without materially 

 affecting either its growth or its luxuriance. 



Were this the case, however, the quantity and quality of the ash left by 

 the same plant should vary with the soil in which it grew. If one soil 

 contained much lime, another much magnesia, and a third much potash, 

 whatever plant was grown upon these several soils should also contain 

 in greatest abundance the lime, the magnesia, or the potash, which 

 abounded in each locality — and the nature, at least, of the ash, if not 

 its proportion, should be nearly the same in every kind of plant which 

 is grown upon the same soil- 

 Careful and repeated experiments, however, have shown— 

 1°. That on whatever soil a plant is grown, if it shoots up in a 

 healthy manner and ftxirly ripens its seed, the quantity and quality of 

 the ash is nearly the same ; and 



2°. That though grown on the same soil, the quantity and quality of 

 the ash left by no two species of plants is the same — and that the ash 

 differs the more widely in these respects, the more remote the natural 

 affinities of the several plants from which it may have been derived. 

 Hence there is no longer any doubt that the inorganic constituents 

 contained in the ash are really essential parts of the substance of plants, 

 — that they cannot live a healthy life or perfect all their parts without 

 them, — and that it is as much the duty of the husbandman to supply 

 these inorganic substances when they are wanting in the soil, as it has 

 always been considered his peculiar care to place within the reach of 



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