81 
GARDENING AS A SCIENCE. 
No. IV. 
There is no one subject in the science of Horticulture which involves so many 
difficulties as the method by which plants receive and elaborate nutriment, so as 
to increase in volume and at the same time deposit within certain vessels or cells 
the peculiar fluids which characterise, and are specific to each individual. 
These are received notions which have been adopted, and appear to satisfy 
most persons; yet we must admit that the whole process is surrounded with 
inextricable difficulties, which perhaps may never be removed ; but there are a 
few simple truths that, if duly investigated, will evince that a great deal too much 
has been incautiously taken for granted. 
The term Sap is perfectly familiar to every one : it is supposed to be the prime 
source and origin of all nutriment ; that it is prepared, first, in the ground, then 
passes into, or is attracted by, that most recently formed and porous termination 
of each fibre of the root, which we are taught to style Spongiole or spongelet, 
and is conveyed thence by some propelling power upwards, to and through every 
organ of the plant, which it thus supplies with appropriate food. 
One truth we admit to exist in this general theory, — it is this ; that some fluid 
or other is taken up by the roots, which is essentially vital to life, and without 
which, every plant that is attached by roots to the ground must inevitably perish ; 
in proof of this, we have only to appeal to the effects which are traceable from the 
action of a due supply of rain, or of water given artificially to a vegetable parched 
with drought. So self-evident are the results, that it would be a waste of time to 
insist upon their reality ; but at this admission we stop, and at this place offer to the 
consideration of the candid inquirer a few lines from an article by Professor Henslow, 
which, being written in plain and homely language, are extremely apposite to the 
present purpose. Writing upon the sap of plants, Mr. Henslow says :— 
" The crude sap introduced at the roots consists of nearly pure water, containing 
only a very small and variable per-centage of certain saline, earthy, and gaseous 
matters in solution. It is a very common opinion, and one upon which most 
erroneous notions are sometimes built by practical men (gardeners and others), 
that this crude sap is directly employed in the nourishment and development of 
the various parts of the plant. There is much plausibility in such an assumption. 
Every one acquainted with the practice of pruning, is aware that, by cutting away 
some parts of a plant, he contrives to throw the rising sap into other parts ; and 
he finds that in consequence of such treatment, these latter parts are better 
nourished, and become more developed than they otherwise would have been ; but 
in spite of so plausible an experiment, the crude sap is not nutritious ; we might 
as well declare that we can receive nourishment from a weak dose of Epsom salts, 
vol. x. — no. cxn. m 
