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- 

 venes 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 interchange 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 



