ASSIMILATION OF FREE NITROGEN 397 



Podocarpus are also able to assimilate free nitrogen by the same means. 

 Hellriegel's results have been confirmed by many observers, and Prazmowski, 

 Schlosing and Laurent, Nobbe, and others have shown that in the absence 

 of root-tubercles the Leguminosae are as little able to assimilate free 

 nitrogen as are other Phanerogams \ Frank's contradictory results were 

 probably due to the presence of nitrogen-assimilating micro-organisms in 

 the soil. 



Certain Leguminosae may assimilate nitrogen in such abundance as to 



FIG. 60. The plants are grown (O) in soil containing hardly any combined nitrogen, to which (KP) potassium 

 phosphate and (KPS) potassium phosphate and nitrate are added. The other ash constituents are already 

 present, and also traces of combined nitrogen, so that feeble devel opment is possible in (O). (After Wagner, Die 

 rationelle Diingung, 1891, 2. Aufl., p. 13.) 



develop normally without being supplied with any nitrogen-compounds. 

 This may be seen in Fig. 60, in which peas supplied only with ash con- 

 stituents (KP) develop almost as luxuriantly as when saltpetre is present 



of Podocarpus, cf. Janse, Ann. d. Jard. hot. d. Buitenzorg, 1896, T. XIV, p. 66. It has yet to be 

 determined whether certain mycorhizal structures are able to assimilate free nitrogen. 



1 Prazmowski, Versuchsst., 1891, Bd. XXXVIII, p. 5 ; Schlosing et Laurent, Ann. d. 1'Inst. 

 Pasteur, 1892, T. vi, pp. 65 and 827 ; Nobbe, Versuchsst, 1893, Bd. XLII, p. 467 ; 1894, Bd. XLV, 

 p. 155 ; 1896, Bd. XLVII, p. 266. Further literature by Stutzer, Centralbl. f. Bact., 1895, Abth. ii, 

 Bd. I, p. 72. 



