THE MAGAZINE 
OF 
THE SCHOOL OF AGRICULTURE, 
COLOMBO, 
Added as a Supplement monthly to the "TROPICAL AGRICULTURIST* 
The following pages include the contents of the Magazine of the School of 
Agriculture for February : — 
THE NUTEITION OF PLANTS. 
BY C. DkIEBEBG, B.A., F.H.A.S. 
That plants feed in some way and supply them- 
selves with the nutriment necessary for growth is a 
fact known to everybody, but the manner in which 
food is assimilated and the form in which the various 
ingredients are taken into the plant — these facts are 
not so generally known. The food of plants may be 
either gases or liquids; they may never be solids. 
How then, some may ask, are solid particles of 
mineral matter found in plants ? Not long ago a 
correspondent to a local paper desoribed the pheno- 
menon of a tree, in the centre of which a large deposit 
of ' sand ' was found, and attempted to explain this 
uncommon occurrence by saying that the sand had pro- 
bably been taken up with the water through the roots" 
Now this explanation must be set aside as totally in- 
correct. The solid mineral matter must have been 
taken into the plant (in combination) in a liquid form, 
and the deposition made after the liquid found its 
way into the interior of the plant; In this manner is 
it that the Diatoms contain silica, and the Oharoe car- 
bonate of lime. The silica most probably was taken 
up in the form of a solution of silicates, and by chemi- 
cal reaction within the plant deposited as the oxide. 
Thus the water with the mineral matter is got from 
the soil and taken up through the roots. The atmosphere 
is another source of plant food, which enters the plan^. 
in a gaseous form. The atmospheric food consists 
principally of carbonic acid gas, with smaller quantities 
of arnmonh gas and water vapour. The mineral 
matter enters through the roots generally as salts, and 
The chemical elements which enter the plants as com- 
pounds may be afterwards broken up into their ele- 
ments and re-arranged to build up new compounds 
to suit the requirements of the plant. The process 
of taking in the crude materials of plant food is called 
assimilation, that of re-arranging the chemical elements 
(which go to form this crude material) to build up 
organic compounds is called elaboration. And herein lies 
the great difference in the mode of nutrition of plants 
and animals, that whereas the plant has to elaborate 
organic food out of inorganic matter, the animal takes 
in its food as organic matter. (To this rule there 
are a few exceptions which we cannot wait to con- 
sider now.) The water with the mineral matter in 
solution is called the " crude sap," and the ela- 
borated organic material which circulates through the 
plant bearing nutriment to every part just as the 
blood carries nutriment to every part of the human 
body, is called the "elaborated sap." 
But how is it that the gases in the atmosphere 
and the mineral matter in solution, taken up from 
the soil, enter the plant? In the epidermis of the 
leaves are the stomata, spaces between two cells 
known as the " guard cells " which regulate the 
opening and shutting of the stomata. Through the 
stomatic apertures the gases in the atmosphere are 
taken up. The water and mineral matter, it has been 
stated, are taken up by means of the roots. The 
taking in of water by the roots depends on the pro- 
cess of diffusion or osmose. The cells forming the 
growiug point or protomeristem of roots (and also of 
stems) are entirely filled with dense protoplasm. The 
cells lying behind the growing point contain less 
it must be borne in mind that neither through the , pro toplasm and more water (cell-sap). Still further 
leaves as gases, nor through the roots as liquids, do j f rom the growing point, in the region of permanent 
plants take up any chemical elements. The element tisme> the cellf5 are fllled principally with cell-sap, 
nitrogen is not taken up as such but as ammonia gas 
or nitrates or nitrites, through the leaves and roots. 
i.e., water containing nutrient substances in solution, 
with little or no protoplasm. By the aotiou of dilfn 
