GARDENING AS A SCIENCE. 
251 
watery solution :— tliey can do no such thing, — but they have the power by vital 
action to stimulate the decomposition of water, and thus to impel a current of 
electricity, which decomposes vegetable or animal remains, and simultaneously forms 
many gaseous compounds, soluble in water, colourless and tasteless : these also 
combine by the specific attractive power of the roots with alkalies and other inorganic 
salts, and pass with them (impelled doubtless by electricity) into the vascular 
tissue, and carry forward and upward the ascending sap. 
Sap^ therefore, is a very delicate and weak solution of carbonic acid, hydro- 
carbon, and saline matters, dl\ derived from the soil^ and susceptible of infinite 
modifications within the cellular tissue of the plant. By analysis some faint traces 
of saline matter can be found in sap, as it flows from the vine and birch ; but it is 
futile to adduce such experiments ; because pure ascending sap cannot be obtained 
free from admixture with the laborated juices of the stem; let us see then how far 
the leaves may operate when properly developed, 
" We know," says Liebig, " that the functions of the leaves and other green 
parts of plants are to absorb carbonic acid, and with the aid of light and moisture to 
appropriate the carbon. But the new products arising from this continual assimi- 
lation are no longer employed by the perfect leaves in their own increase : they 
serve for the formation of woody fibre, and all the solid matters of similar com- 
position. The leaves noto produce sugar, starch, and acids which were previously 
formed by the roots, when they were necessary for the development of the stem, 
buds, leaves, and branches of the plant." 
" A peculiar transformation of the matters contained in bit planxs takes place 
in the period between blossoming and the ripening of the fruit ; new compounds 
are produced which furnish constituents of the blossoms, fruit, and seeds." 
While we admit as general facts the data thus laid down, we must not forget 
our ignorance of the vital principle. That may be, and probably is, of the nature 
of that ethereal light, which for want of a proper title we style electricity : its 
source is the sun, and its intermedia are living vegetables, which connect it with 
the earth. The entire machinery is perfect ; and thus each plant, during its term 
and course, is enabled to attract, absorb, transform, and excrete. Of minutiae we 
are ignorant, but all the work is beautiful, and the smallest atom, even in a state 
of decay, is destined to be reunited to active, living " organisms," wdiich again per- 
form their part in the eternal circle. The electrical development of gases from 
water, and solid matters, and theii* reconversion in fluid and solid modifications, 
rank chief among the wonders which it ]ias been the privilege of modern chemistry 
to reveal. 
