720 CHEMICAL PROCESSES IN THE PLANT. 



only the regeneration of the proteids which is dependent, as in the Papilionaceae, in the 

 manner above mentioned upon light, that is, upon assimilation ^ 



The existence of asparagin has also been proved in the leaves and stems of some 

 plants (see Husemann, Pflanzenstoffe) ; and its presence in the underground perennial 

 parts of Stigmaphyllon jatrophoefolium almost gives the impression of its being there also a 

 reserve-material. 



The absorption of assimilated substances into the plant from without takes 

 place in seedlings, the reserve-materials of which are contained in the endosperm, 

 in parasites'^, and in saprophytes which contain no chlorophyll. Seedlings, which 

 have been most studied in this respect, show how the reserve-materials of the endo- 

 sperm may pass into the absorbing organs (in this case almost always foliar struc- 

 tures) without there being any actual continuity of the absorbing organ with the 

 endosperm; they only lie in close apposition, and can be separated without any 

 injury^ (as in Ricinus^ Fig. 471). It cannot be doubted that the metamorphoses 

 which take place in the nutrient endosperm are brought about by the absorbing 

 organ, that is by the embryo itself; the behaviour of the endosperm of the germi- 

 nating Date, which is absorbed by the delicate tissue of the absorbing organ belong- 

 ing to the cotyledon, shows clearly that the hard thickening-layers of the cell-walls 

 of the endosperm are first of all transformed into sugar under the influence of this 

 organ, and then absorbed. A substance evidently passes out of the absorbing organ 

 into the endosperm which causes this metamorphosis of the cellulose. The oil and 

 albuminoids of the endosperm are at the same time taken up into the embryo, 

 where all the conducting parts of the parenchyma are filled with sugar and starch 

 as long as the endosperm is not entirely absorbed. In the same manner also 

 in Grasses substances possibly pass out of the embryo into the endosperm, and 

 there bring about the chemical metamorphosis and solution of the starch and albu- 

 minoids before they are absorbed by the scutellum which is applied to the surface 

 of the endosperm. It is possible however that in this case there may be some 

 means in the endosperm itself of bringing about the solution of the starch and 

 gluten in the presence of water independently of any chemical action of the 

 embryo. 



The absorbing roots of parasites penetrate into the tissue of the host, and 

 often grow into it in the most intimate manner. It is certain that the exciting 

 cause of the transport of the products of assimilation from the host to the parasite 

 resides in the latter; the parasite acts on the conducting masses of tissue of the 

 host like a growing bud of the host itself; the food-materials penetrate into it 

 because it consumes and changes them. 



The influence exerted by the absorbing organ of the embryo on the substances 



^ [See Schulze, Ueb. Zersetzung und Neubildung von Eiweissstoffen in Lupinenkeimlingen, 

 Landw. Jahrb. VII, 1878.] 



2 Parasites which contain chlorophyll, like the Loranthacese, can themselves assimilate, and 

 only require therefore to draw water and mineral substances from their host (see Pitra in Bot. Zeitg. 

 1861, p. 3). Those parasites which are apparently destitute of chlorophyll (like Orobanche), and 

 saprophytes (as Neottia), contain, according to Weisner (Bot. Zeitg. 1871, p. 37), traces of chlorophyll, 

 which however can hardly be taken into account in assimilation. 



^ For further details see the accounts given by me in Bot. Zeitg. 1862 and 1863, of the 

 germination of different plants. 



