126 VEGETABLE PHYSIOLOGY 
because, in its early stages at any rate, the nutrition of the 
young plant is not complicated by any absorption from 
the surrounding medium, such as sometimes rapidly super- 
veneg on the emergence of a shoot from a tuber or a fleshy 
root. We find the seed contains in some part or other of 
its substance, sometimes even in the embryo itself, examples 
of great classes of food-stuffs which are the same as those 
on which animal protoplasm is nourished, and whose presence 
renders seeds such valuable material for animal consump- 
tion. As these disappear during the development of the 
young plant, which thus evidently grows at their expense, 
we cannot doubt that they form its food, and that vegetable 
protoplasm is essentially identical with animal, at any rate 
so far as its methods of nutrition are concerned. Proteins, 
carbohydrates, fats or oils, together often with certain 
other bodies which are less widely distributed, are the 
materials which, in various forms, are met with. 
But to be sure that these complex substances are the 
food of all plants, we must ascertain whether they can be 
found in the cells of those plants and parts of plants which 
we find absorbing the simple inorganic materials of which 
we have spoken. If we study the protoplasm of a living, 
active, vegetable cell, and treat it with appropriate solvents, 
we can extract representatives of them, or of some of them, 
from its substance, in the interior of which they are held 
sometimes in solid amorphous form, sometimes in fine 
suspension or in actual solution. The nutrition of the 
protoplasm can only take place when these substances are 
brought into the most intimate relations with it; from 
them, no doubt, in ways not yet discovered, it builds itself 
up, and by its own decomposition it reproduces many of 
them. The details, however, of the mterchange of matter 
between the living substance and its food, the way in 
which the latter is transformed into the former, are points 
about which almost everything essential remains still to be 
discovered. 
But while we recognise that the ultimate nutrition of 
