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GARDENING AS A SCIENCE, 
VEGETABLE PHYSIOLOGY.— No. VIIL 
Functions op the Leaves. In the Article No. VII. some idea was conveyed 
of the products of vegetable organization, leading to the inevitable inference that, 
animals entirely, and the human species to a very great extent, are indebted for 
their chief sustenance, and many of their essential comforts, to those multiform 
products. 
The uses of analysis are very great. We are not among those who attach 
implicit credence to all the theories of the Chemist, because it is impossible to 
bring the vital functions to the test of his re-agents, A plant, living and growing — 
its roots fixed to, and wandering within their appropriate bed of earth ; and its 
superior developments revelling in the atmosphere of heaven, — is not, nor can ever 
be rendered the legitimate subject of chemical investigation. It is the office of the 
laboratory to rend to pieces, and to destroy ; to extinguish life, while in search of 
the elements of its products ; therefore, every experiment with cuttings, detached 
portions, or even with entire plants raised from the soil, is an unnatural process ; 
one which either destroys life, or investigates its offices under altered conditions. 
But when the Chemist operates upon gums, resins, sugar, or the fabric of woody 
tissue, his course is legitimate, and he then correctly arrives at those conclusions, 
which it was the object of our last article to point out. 
Presuming, therefore, that without exception, every known vegetable product 
is resolvable into the elements carbon, oxygen, and liydrogen, with or without 
nitrogen ; we may safely search for causes, or first principles, and inquire whence, 
and through what mechanism, a plant has derived the substances which, by any 
possibility, can furnish those ultimate elements. 
The Atmosphere consists of four-fifths of the air or gas called Azote or 
Nitrogen, and one-fifth of the gas called oxygen in round numbers ; — these are its 
indispensable components. 
The two gases, so united, constitute breathing or respirable air ; but with them 
floating in the volume are uncertain portions of other gases — carbonic acid, 
hydrogen, watery vapour, and a trace of ammonia, which affect the quality and 
salubrity of the air. 
Water, in the state of a liquid, is said to be composed of hydrogen and oxygen 
— two volumes of the former to one of the latter, held together (according to 
Dr. Faraday) by a quantity of electricity, so vast, as to startle and confound the 
imagination. "Water, however, as such, like similar compounds, is not oxygen and 
hydrogen. By the action of the voltaic battery, it is made to 7/ieId those gases ; 
and, vice versa, the elements so developed can, by the electric spark, and by other 
processes of combustion, be re-united in the form of water. Such processes of decom- 
position and re-union furnish the most conclusive and beautiful evidences of 
VOL. XI. NO. CXXVIII. A A 
