326 



LECTURE XX. 



have shown, is widely spread in the vegetable kingdom, especially in growing shoots 

 and perennial root-stocks and tubers. It is of course still questionable whether the 

 asparagin arises in these organs by synthesis, to be converted by further synthesis and 

 the assumption of sulphur into proteid substances. That something of the sort 

 actually occurs under certain circumstances Pfeffer has demonstrated with seedlings 

 of Lupins, etc. In these cases, however, the asparagin itself had previously arisen 

 by a splitting up of the proteid substances of the seed ^. At any rate the possibility 

 exists that in many cases asparagin may be formed in the first place from carbo- 

 hydrates and nitrates, to be converted later, with the assumption of sulphur from the 

 decomposition of a sulphate, into proteid substances. That, conversely, asparagin 

 arises from the proteid substances of many germinating seeds (e. g. Lupinus), root- 

 stocks, and tubers (e. g. Potato), to be subsequently reconverted into proteid, when the 

 green organs begin to assimilate, cannot be doubted from the researches of PfefFer, 

 Schultze, and others. 



It is now decided that all the various carbo-hydrates, fats, and proteid substances 

 of the plant are derived from the starch assimilated in the chlorophyll. This is 

 practically equivalent to saying that all the organic substances necessary for the 

 construction of the cells and organs of the plant, are to be referred to the activity 

 of the assimilating chlorophyll, since the plant requires for the construction of 

 cells and organs generally only these three groups of materials. I have consequently 

 classified them '-is the constructive materials of the organs, in contrast to all other 

 organic substances of the plant. Seeds or tubers, bulbs, rhizomes, buds of trees and 

 even spores — the unicellular reproductive organs of Cryptogams — may be made 

 to develope new roots and shoots, and occasionally even flowers, by growth, though 

 no other materials are placed at their disposal than pure water and the oxygen of the 

 atmosphere : the latter however is only necessary for respiration, by which means 

 a considerable portion of the organic substances is completely destroyed. Since now 

 all the parts of plants above named — which we term reservoirs of reserve-materials, 

 because the materials for germination in the widest sense are stored up in them 

 — contain essentially only proteid substances, carbo-hydrates, and fats, or it may 

 be only proteids and fats, as in many seeds (Ricinus, Brassica, Cucurbita, Almond, 

 etc.), it is obvious that the new roots and buds are able to develope as the 

 substances mentioned are used up in growth. This is still more obvious when 

 the development of seedlings is allowed to take place in profound darkness, where 

 assimilation cannot come into consideration at all ; or when the developing seedlings 

 are left in an atmosphere from which every trace of carbon dioxide has been withdrawn. 

 At the conclusion of such a process of germination, the reservoirs of reserve-materials 

 are emptied, and when the growth finally ceases, no nutritive matters being admitted 

 from without and no assimilation taking place, we have before us a new plant which 

 consists of cellulose walls and relatively small quantities of protoplasm, cell-nuclei, 

 and chlorophyll-grains (etiolated or not). These constituents of our young plant 

 have been produced from the reserve-materials, proteids, carbo-hydrates, and fats, with 

 the aid of the water and oxygen taken up. Of the two groups last named, how- 

 ever, a considerable quantity has been completely destroyed during the growth, by 



' Cp. Sachs' ' Lehrbtuh der Botanik,' IV. Aufl., p. 690. 



