Latham : Assimilation of Sterigmatocvstis 237 



nitrogen and, furthermore, had no part in aiding the action of the 

 host In the case of Phoma, Saida * confirms Puriewitsch's con- 

 elusions with regard to the proportion between the amount of 

 nitrogen brought into combination and the sugar at hand; and 

 moreover, he records that when the fungus is growing on a solu- 

 .tion poor In nitrogen compounds, then the CO^ evolved becomes 

 greater, that is, a greater expenditure of energy is indicated. 

 Ternetzf found a gain in combined nitrogen due to the activity 

 of a fungus isolated from the roots of Oxycoccus. 



■This summary of the work done on the relation of fungi to 

 nitrogen-fixing is intended to touch the main points only. The 

 literature may be had in detail from the works of Czapek % and 

 Lafar § and we are therefore content with this brief citation. The 

 same question with bacteria has, oi course, been more widely 

 worked over, but with it we have made no attempt to deal. 



In our former work, gaseous chloroform was the reagent used 

 as a stimulant, but in this case we had recourse to zinc sulphate 

 in solution, a stimulant with which Richards || had earlier worked. 

 This was both because the difficulties in manipulation with the gas 

 added to those of Kjeldahl analysis would probably have taken 

 more time than we could hope to give to the work, and also because 

 zinc sulphate has been more often used as a stimulant and its action 

 is better known. The principle in each case is the same so that re- 

 suits would be similar. Aside from the difference In stimulant, the 

 same methods were used as previously, the same superior reagents 

 and insoluble glass, and the same care in preparation. A careful 

 plate culture was prepared with the nutrient media in the gelatine to 

 test the purity of the Sterigniatocystis. This showed no trace of 

 bacteria whatever, so it was concluded that the spores were bac- 

 teria-free or at worst so little contaminated as to be highly satis- 

 factory for our work. The growing cultures were kept under 

 sealed bell jars in order to exclude influences other than the one 

 under observation, since we had found that the fungus is very sen- 



* Saida, K. Loc. cit, 



I Ternetz, C. Assimilation des atmospharischen Slickstoffs durch einen torfbe- 



wohnenden Pilz. Ber. Deuts. Bot. Gesells. 22 : 267. 1904. 

 \ Czapek, F. Loc. at, 

 \ Lafar, F. Loc, ciL 



II Richards, H. M. Loc. cii. 



