336 ASSIMILATION. 



higher plants ; namely, (1) that in favor of the chlorophyll cells, 

 (2) that in favor of the conductive tissues of the petiole and 

 stem. So far as analogy drawn from the lower plants is con- 

 cerned, one of these views is as tenable as the other ; for while 

 in a simple alga all the formation of new protein matters must 

 go on in a cell where there is chlorophyll or its equivalent, in 

 the case of a fungus, nourished as in the experiments of Pasteur 

 upon a simple ternary body and a nitrate, the process must of 

 necessity take place in cells where no chlorophyll is present. 



882. Exact observations upon the subject of the formation of 

 albuminous matters in the plant are not abundant. Reference will 

 be made here chiefly to those by Emmerling, who carried on an 

 extended series of investigations with Vicia Faba. He examined 

 all parts of the plant with respect to the inorganic nitrogen com- 

 pounds furnished, and then sought for the protein compounds 

 resulting therefrom. His results are interpreted as showing that 

 the nitric acid which is absorbed from the soil, and can be detected 

 in all parts of the roots and steins, disappears very rapidly in 

 the leaves and all parts which are actively growing, so that there 

 is found only a mere trace in them. According to him, it is in 

 green leaves that the transformation of nitrogenous matters takes 

 place. The first product of this transformation is not at present 

 certainly known ; but there is good reason to regard it as a mem- 

 ber of the group of carbamides. 1 Those parts of the plant which 

 are rapidly growing are much richer in amides than the older 

 and more fully developed portions. This fact is shown by 

 Kellner 2 to be true of pasture grass, in which the amides are 

 more abundant in the young than in the old parts. 



APPROPRIATION OF SULPHUR. 



883. The amount of sulphur which exists as an essential part 

 of the albuminous matters of the plant is quite small, being not 

 far from one per cent. 8 



884. As already shown (681), sulphur is taken into the 

 plant in the form of sulphates, chiefly calcic. The calcic sul- 

 phate 4 is probably decomposed by the oxalic acid produced by 

 the plant, and thus an insoluble calcic oxalate is formed ; then 



1 Versuchs-Stationen, xxiv., 1880, p. 113. 



2 Centralbl. f. Agnc.-Chem., 1879, p. 271. 



8 Ranging, according to Ebermayer, from .4 to 1.8 per cent ( Physiologische 

 Chemie der Pflanzen, 1882, p. 616). 

 * Holzner : Flora, 1867. 



