462 CONSTRUCTIVE AND DESTRUCTIVE METABOLISM 



product of metabolism 1 , but a supply of sugar may suffice to partially 

 or completely inhibit the formation of this compound, or even to induce an 

 assimilation of ammonium salts and a synthetic formation of proteids 

 (Sects. 66, 67, 70). 



It is hence easy to see why a much less marked accumulation of 

 amides occurs during the germination of seeds which contain an abun- 

 dance of starch or oil, than in that of leguminous seeds which are rich 

 in proteids. In the latter case it is only as starch is formed that the 

 accumulated asparagin, &c. is regenerated into protcid substance and hence 

 gradually diminishes 2 , for when the seedling is kept in air deprived of 

 carbon dioxide the assimilating organs of L npinns, &c. remain loaded with 

 asparagin until death occurs 3 . Under these circumstances the phosphates 

 and sulphates set free by proteid-decomposition must remain unassimilatcd 

 so long as no reconstruction of proteid is possible 4 . 



It is apparently of considerable economic importance that amides, 

 phosphates, &c. should be stored up in these forms only when the quantities 

 present are small. In the case of leguminous plants, on the other hand, more 

 material can be condensed into a smaller space in the form of proteids, and 

 hence a supply of nourishment is provided sufficient to enable the seedling to 

 develop in a non-nitrogenous soil until it is able to form root-tubercles and 

 thus assimilate free nitrogen (Sect. 69). The stored proteids not only afford 

 a supply of food but their decomposition renders a certain amount of 

 energy available, no matter whether the liberated non-nitrogenous sub- 

 stances are used in respiration or as plastic or constructive material. 

 The latter may occur when other non-nitrogenous reserve-materials are 

 present, although in the case of the Lcguminosae this is a point which has 

 not yet been satisfactorily determined. 



When proteids are continually assimilated and disintegrated, the nitro- 

 genous waste products must be excreted and thus any over-accumulation 

 prevented. In the case of Fungi this is provided for by the excretion of 

 ammonia, and in the case of animals by that of urea. The latter is, however, 

 formed by synthesis from ammonium carbonate 5 , and hence in both cases 



1 Nageli, Bot. Mitth., 1881, Bd. in, p. 283; 'Wehmer, Bot. Zeitung, 1891, p. 295; Marchal, 

 Centralbl. f. Bact., 1895, Abth. ii, Bd. I, p. 753. The formation of ammonia during putrefaction 

 is well known. 



a Pfeffer, Jahrb. f. wiss. Bot., 1872, Bd. VIII, p. 548; E. Schulze, Landw. Jahrb., 1880, Bd. IX, 

 p. 44 ; 1888, Bd. xvn, p. 691. 



3 Pfeffer, Monatsb. d. Berl. Akad., 1873, p. 780. The mode of experimentation is represented 

 in Fig. 48. These results have been confirmed by O. Mu'ller, Versuchsst., 1887, Bd. XXXIII, p. 326. 



4 For sulphates, cf. E. Schulze, Landw. Jahrb., 1876, Bd. v, p. 856 ; 18.80, Bd. IX, p. 21 ; 1892, 

 Bd. xxi, p. 118; Kellner u. Sachsse, Phytochem. Unters., 1880, I, p. 58; Tammann, Zeitschr. f. 

 physiol. Chemie, 1885, Bd. IX, p. 417. During proteid-decomposition, amides and sulphates increase 

 concomitantly, and, as in animals, sulpho-acids are probably formed at the same time. Cf. Sect. 74. 



5 Bnnge, Physiol. Chemie, 1894, 3. Aufl., p. 296. 



