ASPERGILLUS NIGER GROUP 



221 



differ from ^4. foetidus as follows: primary sterigmata are reported to be 

 12 to 20/x by 4.4 to 9m in contrast to secondaries 7 to 10/x by 2.5 to 5/x, whereas 



Fig. 63. Conidia, Aspergillus niger group. A , Single long chain of conidia, X 1000 

 (Photograph by Edward Yuill). B, Conidia of a typical strain of A. niger, NRRL 

 No. 344, X 700. C, Conidia of the citric and gluconic acid producing strain, NRRL 

 No. 67, X 700. The large size and coarsely roughened walls are characteristic of 

 the conidia of the latter strain. 



in A. foetidus both series measure 7 to 10/x by 2 to 4m; conidia are globose 

 3.7 to 5.6m in diameter. 



The species repeats the colony appearance of certain mutants produced 

 by means of chemical stimulants by Thorn and Steinberg (1939) from the 

 latter 's standard strain of A. niger. 



