1Q20] 



BRIEFER ARTICLES 



467 



TABLE I — Continued 



Solution 



Co(X0 3 ) 2 /flask 



0.1 mg. . . 



0.5 



1 



10 



20 



50 



Ua(NO,) a /flask 



0.1 mg. . . 

 1 



5 



10 



20 



50 



(gm.) 

 0.075 

 0.103 

 O.093 



o. 190 



0.180 

 0.192 



0.062 



0.053 



0.053 



0.138 



(0.462) 



0.095 



Sporulation 



o. 1 mg. Zn/liter-f-Co (NOa)-; 



Practically sterile 



Fair 



Fair 



Excellent 



Excellent 



Excellent 



o. r mg. Zn/liter-f U(MN03)2 



3-4 



Practically sterile 



3-4 



Practically sterile 



3-4 



Practically sterile 



3-4 



Fair 



2-3 



Fair 



3-4 



Practically sterile 



exist between increase in dry weight, increased acidity, and decrease in 

 sporulation. 



Examination of the data obtained with Co(N0 3 ) 2 +6H 2 and with 

 U0 2 (N0 3 ) 2 +6H 2 shows the surprising result that the phenomenal 

 increases in dry weight ascribed to these metals do not occur. 2 The 

 increases in dry weight, excepting for a few cases (zinc plus cobalt salts), 

 are within the experimental error of the observations. The unincreased 

 acidity of the cultures supports the viewpoint that no increases in growth 

 had been obtained. As concerns sporulation, there seems to be no regu- 

 larity in the cultures containing cobalt or uranium, and while it is inter- 

 esting to note that in the last series, containing only cobalt and uranium, 

 sporulation took place, it would be an error to suppose that this 

 necessarily implies that neither zinc nor iron is needed by A. niger for 

 spore formation. The probable explanation is the presence of traces of 

 iron and of zinc in the cobalt and uranium salts. 



The lack of any marked increases in dry weight brought about by 

 the addition of cobalt and uranium salts to the cultural solution is 

 entirely contrary to the results already recorded in the literature. The 

 explanation apparently best fitting the facts is that partial replacement 



2 Le Pierre, C, Remplacement du zinc par l'uranium dans la culture de V Asper- 

 gillus niger. Compt. Rend. 156:156. 1179. 1913; Richards, H. M., Die Beeinflus- 

 sung des Wachstums einiger Pilze durch chemische Reize. Jahrb. Wiss. Bot. 

 30:665. 1897. 



