630 CHEMICAL PROCESSES IN THE PLANT. 



Small admixtures of oily matter appear to be never absent, and in some cases, 

 especially in many seeds, this alone is present without any carbo-hydrate (as the 

 almond, gourd, castor-oil plant, &c.). 



Together with albuminoids, carbo-hydrates, and oils, a variety of other com- 

 pounds may also occur in the reservoirs of reserve-material ; but the limitation of 

 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 still w^anted 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 w^ater 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 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 con- 

 tained in the reservoirs of reserve-material reappear as such in the protoplasm of the 

 newly-formed organs, having, independently 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) ; w^hile 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, inuline, and oil are the sub- 

 stances from which are formed the cell-w^alls 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 whole 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 sub- 

 stance is also entirely destroyed and converted into carbon dioxide and w-ater, 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, inuline, and oil, are 

 of the same physiological value wath 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 Allium 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 however 



