1903.] with especial Reference to its Nitrogenous Metabolism. 475 



when offered in the form of ammonium salts, while the latter alone 

 could assimilate nitrate nitrogen. Artari,* working with the gonidia 

 •of two lichens, isolated in pure culture, showed that, after peptone, 

 asparagine and ammonium sulphate were the useful sources of nitrogen 

 for these algae, and other observers f have made equally careful experi- 

 ments in the case of some of the higher plants, and have shown that 

 not only simple ammonium salts, but also compound ammonias, such 

 .as methylamine, ethylamine, can readily be assimilated. 



From a physiological point of view Chlorella pyrenoidosa must be 

 included in this second class, for it has been shown, as the result of 

 quantitative as well as qualitative experiments, that this alga prefers 

 its nitrogen to be presented to it in the form of ammonia or ammo- 

 niacal compounds. Among the latter urea, uric acid, &c, rank high 

 in nutritive value. 



It would also appear from the foregoing chemical experiments that 

 this ammonia, after being absorbed by the cell, is elaborated into 

 albuminoid ammonia, \ a term used to describe certain nitrogenous 

 bodies of ammoniacal nature, which yield ammonia when boiled 

 with alkaline permanganate of potash ; in fact, almost all the 

 nitrogen assimilated would appear to remain in this comparatively 

 simple form, This nitrogen, for example, is more easy of attack than 

 that contained in uric acid. These elaborated, nitrogenous compounds 

 appear to be retained wholly within the cell body, but under certain 

 conditions, only observed in the case of " older " cultures, they seem 

 to escape from the cell, and can be traced free in the liquid. 



The presence of glucose in a culture liquid frees the alga from the 

 necessity it would otherwise experience of manufacturing carbohydrate 

 for itself. The algal cell, being thus relieved of a certain part of its 

 ordinary work, appears to be enabled to reproduce itself much faster, 

 .and its nitrogen assimilation is also much increased, though, owing 

 to the increased multiplication of cells, it would be impossible to say 

 that the nitrogen assimilation per cell was increased. The chlorophyll 

 body of the cell, at the same time, gives evidence that its function has 

 been interfered with by a most striking change in form and in the 

 amount of chlorophyll. It is distinctly noteworthy that neither cane- 

 sugar nor lactose can be substituted for glucose in this connection. 



The effect of glucose in causing a definite change in the chlorophyll 

 body, and in generally stimulating growth, would not appear to be an 

 isolated fact. It has been shown by other observers in the case of three 

 green algae (Chlorothecium saccharophilum, Chlorella protothecoides, Sticho- 

 coceus bacillaris), upon whose nutrition the effect of glucose was 



* ' Bull. d. 1. Soc. Imp. des Nat. de Moscou,' 1899, p. 39. 



f Laurent, ' Ann. de FInsfc. Past.,' vol. 3, 1899 ; Lutz, ' Coinptes Eendus,' 

 vol. 126, p. 1227. 



X Wanklyn, ' Chem. Soc. Journ.,' 1867, p. 59. 



