Arboriculture. 65 
light, air, and moisture, are essential to its existence, and that no 
sooner is life extinct, than the laws of Chemistry, which hitherto were 
over-ruled by that principle, exert their influence ; — it is decomposed, 
and having passed into its original elements, is fitted for becoming 
the support of other organized beings. 
In these respects plants bear a close analogy to animals ; like them 
too, they are possessed of that inconcei-\-able powei", by means of which 
they are enabled to assimulate, or change into their own substance, a 
\'ariety of extraneous matter. In common with animals, they have the 
power of increasing their species ; many of them possess spontaneous 
motion, or irritability.* Indeed, the lowest link in the chain of vege- 
table beings, approaches so closely to that which holds the same place 
in the animal kingdom, that a well defined line of demarkation has in 
vain been sought for. 
To discover the real natm-e of the food of vegetables, has occupied 
the attention of philosophers for a long period ; nor to this day is the 
problem satisfactorily solved. It would, however, lead me far beyond 
the limits which I have proposed to myself in this outline, to notice the 
conflicting opinions of those who have investigated this difficult sub- 
ject; let it suffice to observe, that the opinion most generally received 
is, that water, together with carbon, (the base of charcoal,) either in 
solution, or combined with an acid, in the form of carbonic acid gas, 
constitute the principal food of vegetables ; and that the application of 
manure, consisting of decaying vegetable and animal matter, to the 
soil, is the only means Avithin our power, of supplying the plant witlt 
the latter of these essential principles. 
The earths, which are only finely divided flint, limestone, alumine, 
(earth resulting from clayslate, and analagous rocks,) and a few others 
of less common occuiTence, do not constitute any portion of the food of 
plants, — -the use of them being merely to afford a medium in which 
the proper food may be administered; and their fitness for this pur- 
pose, depends both on the proportion in which they are combined, and 
the state of division which they have attained. Thus, a soil composed 
principally of silex, (earth of flints,) particularly if some portion of it 
be not in a state of minute division, will not be sufficiently compact to 
retain for any length of time, a pro}>er degree of moisture. A soil, 
consisting of nineteen parts out of twenty, of siliceous sand, Sir Hum- 
phrey Davy found to be absolutely barren ; yet so small a portion of 
finely divided matter, as one part in twelve, he asserts, is sufficient 
to adapt it to cultivation. The qualities whereby this sand may be 
* Hedysai'um Gyraiis, Dionia Muscipvtla, Stylidiiira Glandulosum, Berberis Vulgaris, Kalmia 
Glauca, and the cammou Nettle, and Pelitory of the AVall, are examples familiar to every 
gardener. 
Minerals, observes Linnaeus, increase. — Vegetables increase and live, — Animals, increase^ 
fcnd live, and feel. 
Vol. 1, No. 2. K 
