GROWTH — NUTRITION. 
99 
fixes it as sulphate of ammonia ; it does not act as a stimulant ; 
a plant has no nerves, therefore there can he no substances by 
which a leaf can be stimulated to appropriate to itself a greater 
quantity of carbon from the air, when the other constituents 
are wanting which the plant requires for its development. The 
explanation of the mode of action of gypsum is improbable, 
and the author must show, first, that sulphate of ammonia has 
been formed in gypsum, when long exposed to the atmosphere, 
and why plants should not be capable of stimulation. A con- 
siderable part of the work of the author is devoted to the 
inorganic constituents of plants. He shows their constancy, 
and also, that one constituent supplies the place of another in 
its various combinations ; thus, for instance, it has been proved, 
by the analyses of the fir of different localities, that the num- 
ber of bases is certainly different, but that the quantity of 
oxygen in them is the same. Indeed, it is very probable, 
judging from what the author states, that alkaline bases are 
essentially necessary for the development of plants. These 
constituents of the soil, in general, have the greatest influence 
upon the growth of plants, a circumstance which is elaborately 
investigated in the sections on the culture of plants, on the 
rotation of crops, and on manures. This first part appears to 
me the most important in the work, as belonging to our sub- 
ject ; the second part is purely chemical. 
In the Journal of Practical Chemistry, by Erdmann and 
Marchand, vol. xx. p. 267, we find a continuation of confir- 
matory experiments, on the effect of humic acid bases parti- 
cularly of those prepared from peat as a means of manure^ 
by W. A. Lampadius. The composition consisted of the 
refuse of peat, of chalk-dust, of brick-dust, and ashes, in the 
proportions 53, 3, 3, 3. A development of carbonic acid is 
probably also effected here, through the action of humic acid 
on the chalk-dust. 
Speculations on the sources of Carbon and Nitrogen in 
Plants and Animals, are found in Daubeny’s Lectures on 
Agriculture, and an extract from them appears in the Edin- 
burgh New Philosophical Journal, vol. xxx. p. 360. Daubeny 
directs attention to the fact, that carbonic acid and ammonia, 
491 
