78 



I'lIYSlOWGY OF THE FUSGl 



nutrition may be rewarding. It was unnecessary to resort to elaborate 

 methods of medium purification to demonstrate that manganese is essen- 

 tial for P. gonapodyoides. This situation occurred only when reagent 

 magnesium sulfate of a certain manufacture was used. Substitution of 

 another brand of magnesium sulfate revealed heavy (biological) con- 

 tamination by manganese (Fig. 15). The inoculum was found to carry 

 sufficient manganese and other micro elements to influence the amount of 

 growth in the first passage. No growth resulted in the third passage in 



A B 



Fig. 15. Pythiomorpha gonapodyoides growing in a basal solution \Yith no added 

 mineral supplements. A, medium prepared with Baker's Analyzed magnesium 

 sulfate. B, medium prepared with Mallinckrodt's magnesium sulfate analytical 

 reagent. Age, 5 days. Note the extensive white mj'celium in A and the slight 

 growth in B. (Courtesy of Robbins and Hervey, Bull. Torrey Botan. Club 71: 263, 

 1944.) 



the absence of added manganese. The range of manganese concentra- 

 tions for optimum growth was narrow and appeared to depend upon the 

 concentration of other micro elements present, particularly zinc. Stein- 

 berg (1935) found manganese to be essential for A. niger. McHargue and 

 Calfee (1931, 1931a) noted that growth of A. flainis, Rhizopus nigricans, 

 and Saccharomyces cerevisiae increased in the presence of added 

 manganese. Steinberg (1945) showed that omission of manganese from 

 a balanced medium resulted in a decrease in yield of A. niger from 

 1,084.8 to 356.6 mg. No spores formed when manganese was omitted. 

 It is interesting to note that, as the numbers of spores used for inoculum 



