PV5 
THE SCIENTIFIC HISTORY OF A PLANT. 
too grave a term to be applied here) — a fane}- of vegetable life founded upon a review of Dr. Faraday's 
magnificent discoveries. 
The vitality of a plant forms an episode in the history of discovery, because at the first animal Life 
was regarded as totally distinct from vegetable life ; but as facts accumulated, analogy in functional 
arrangement, though brought about by a different form of organic apparatus, leads us to suppose that 
there was but one known cause of vitality, both in plants aud animals. In a plant, heat and light are 
considered as necessary, but not as the first great moving power. Vegetable physiology advances, and 
seems to incline to the idea that the vitality of a plant is a purely chemical process. 
Upon what is dependent, then, this chemical action that enables a plant to decompose both carbonic 
vitaiityof a piantcon- aom an d wa ter, that is always going on in it as a part of its life, and the source of its 
sidercd as resulting from development ? The magnetic discoveries of Dr. Faraday of the connection between 
magnetism, light, and crystallisation, have no doubt brought us to the eve of a great 
generalisation. We are in a state so happily described by Humboldt as " a state of presagement " — 
in one of those intervals that renders the history of philosophy so indistinct between the presentiment 
of an epoch and its actual realisation. We have the strongest grounds for considering galvanism, 
electricity, maguetism, as one and the same force ; which force is a certain quality of matter termed by 
Professor Graham polarity, which is due to the presence of inherent magnetism. So then, we may 
almost go so far as to say, that the same force that deflects a ray of polarised light — that causes the 
crystal to elect a certain determinate position in the magnetic field — that gives polarity* to the needle of 
Generalisation upon the compass — that this same force causes the formation and growth of an organic 
the vitality of a plant. cell 
Such may be considered as an unfinished and imperfect glance at some of the most striking points 
in the chemical historj- of vegetation ; but our survey is not yet finished. The vegetable flame requires 
the introduction of certain peculiar elements which are not organic, but which nevertheless it makes 
subservient for the support of life, and for the growth of structure. 
We do not now wish to discuss the exact degree of alkalies or alkaline earths required in certain 
Peculiarities of sou eases > nor to trouble ourselves about the presence of organic acids in plants. We know 
are required for differ- that Oaks require certain conditions for their existence ; in some soils they flourish, in 
others they will not live. A barren and granitic soil amply supports the Pine and 
the Fir, but not the Oak • and this because such soils do not contain sufficient alkalies for the purpose. 
The Equisctaeea?, like the Oak, require much potash ; a soil formed from the grauwaekc, and porphyry 
nourishes these plants. 
The Tobacco-plant and the Vine require linie ; the Beet and Potatoes magnesia ; Chcnopodium 
likes nitrates ; and the Fuchsia iodine ; Cereals phosphates of ammonia and magnesia. For the 
growth of these plants, one or other of these constituents is required ; but there are some soils com- 
posed of pure sand and limestone — they support no species of vegetation; they are absolutely barren. 
Argillaceous earths always exist in a fertile soil ; their fertility being doubtlessly derived from the alkali 
they contain, because rich soils were formed by the disintegration of potash and soda felspars. Alumina 
is never found in the ashes of plants ; its action is merely indirect. It is useful in condensing the 
water and the ammonia of the atmosphere. A cubic foot of felspar contains enough potash to supply 
an Oak-copse of twenty-six square feet with potash for five years. 
We find, even in short excursions in our own country, great changes in the scenery of different 
changes of flora. places ; tliis is often brought about by the predominance of a certain class of 
shrubs. We may pass a woody country — a country occupied as arable land — an entirely pastoral 
country. Whence this difference ? From the soil, which influences the productions owing to the 
operations in nature of the facts which I have just stated. Soil, with climate, is omnipotent in 
Boll and climate Influ- influencing the distribution of plants; and the formation of soil and arable land is 
big the distribution one of the main points of agricultural geology. Such a fact furnishes us w il li :i \ rn 
clear example of the connection existing between chemistry, botany, and geology. 
Put how arc soils formed? This is yet a question to be explained. 
In speaking of the imperishability of matter I alluded to the changes which it is constantly under- 
going, because the earth, from the first moment of creation, has been subject to the never-ending play 
of natural forces; and by looking at the present state of the globe, and then by reading ils past bistorj . 
the mutation of all material substance is thoroughly illustrated. 
The progress of disintegration has not been much investigated ; but Liebig has collected into his 
Disintegration has not "Agricultural Chemistry" the results of most experiments on this Subject lie 
bote much investigated, divides the process of disintegration into two groups- -waste. 1 1 it ■ result of mechanical 
force, and disintegration, properly so called, a product of chemical action. It by no means follows that 
of plants. 
