ASSIMILATION AND METASTASIS. 
707 
substances of this kind to particular species of plants shows that they are not 
of the same significance as the former. They may be of great importance for 
the growth of the species; but more accurate knowledge is slill wanted in all 
cases. 
Since seeds, tubers, and other parts of plants that are filled with reserve-material 
can be made to unfold buds, to put out roots, and even to form flowers and the 
rudiments of fruits by supplying them with pure water and oxygenated air when the 
conditions for assimilation (chlorophyll and sunlight) are absent, it follows that the 
substances stored up in these reservoirs furnish the material for the growth of the 
new leaves, roots, and flowers. The reservoirs are therefore emptied in proportion 
as the growth of the new organs progresses ; and when finally they become com- 
pletely empty, all further growth ceases, if sunlight and chlorophyll do not cooperate 
to produce new formative material by assimilation. It is moreover easy to follow the 
reserve-materials by means of micro-chemical reactions in their course from the 
reservoirs through the conducting tissues to the growing organs, and to recognise 
their relation to the growth of particular tissues. A close study leads first of all to 
the conclusion that the albuminoids contained in the reservoirs of reserve-material 
reappear as such in the protoplasm of the newly-formed organs, having, independ- 
ently of temporary qualitative changes, only altered their position. On the other 
hand it shows that the oily matter and the carbo-hydrates which had accumulated in 
the reservoirs finally entirely disappear as such or leave only a small residue (oil) ; 
while in their place a mass of new cell-walls is formed which were not in existence 
before; and the material for the construction of these can only have been derived, 
under the given conditions, from the carbo-hydrates, or, when these are absent, from 
the oily matter which has now disappeared. If we thus come to the conclusion that 
starch, sugar, inulin, and oil are the substances from which are formed the cell-walls 
of plants, at all events in so far as they are nourished from a reservoir of reserve- 
material, it by no means follows from this that the v/hole of the store is used up 
entirely in the production of cellulose ; on the contrary a variety of other substances 
are formed during growth, such as vegetable acids, tannin, colouring-matters, &c., 
which are probably also derived from the same non-nitrogenous reserve-materials. 
A part of the non-nitrogenous substance is also entirely destroyed and converted into 
carbon dioxide and water, a process which may cause a loss of 40 or even 50 per 
cent, of the weight of the organic substance of those seeds which germinate in the 
dark. 
If the reserve-materials stored up in different seeds, tubers, bulbs, &c. are 
compared, it is seen that starch, the various kinds of sugar, inulin, and oil, are 
of the same physiological value with regard to their most important purpose, viz. 
the formation of new organs ; inasmuch as these substances can replace one another. 
Thus the cell-walls of the embryo of Allivm Cepa are formed at the expense of 
the oily matter of the endosperm ; but the cell- walls of the leaves and roots which 
grow from the bulbs evidently obtain their formative material from the glucose-like 
substance which fills the bulb-scales in a state of solution. In the Beet cane- 
sugar is stored up for the same purpose, inuHn in the tubers of the Dahlia, and 
starch in the tubers of the Potato, the bulbs of the Tulip, &c. ; and these are 
subsequently consumed. But in most seeds all these carbo-hydrates are replaced 
z z 2 
