VARIATION 69 



culture No. 113 (XRRL No. 447) of A. oryzae, received from Baarn and 

 believed to stem from Cohn's original strain, is a very floccose, loose-textured 

 culture bearing comparatively few, small, light yellow to tan heads. Co- 

 nidiophores are long, ranging up to 2 to 5 mm., and are very thin- walled. 

 There is only a trace of green even in individual heads, and in general aspect, 

 the culture normally shows no green color. Aspergillus flavus in its typical 

 form is not floccose and is very heavy sporing. Conidiophores arise directly 

 from the substratum in a close stand, are usually 1 mm. or less in length, 

 and are comparatively heavy walled. Colonies are regularly in yellow- 

 green shades and range from light to comparatively dark green (see species 

 description). A. parasiticus Speare goes even farther. Colonies are very 

 dark green in color. Conidiophores usually range from 200 to 400m in 

 length, and sterigmata are typically in a single series, whereas they may be 

 in a single or double series in A . oryzae and A . flavus. In the opposite direc- 

 tion, but markedly different from A. oryzae is A. effusus Tiraboschi. Typi- 

 cally this is very floccose and comparatively light sporing, with heads borne 

 upon short conidiophores which arise from the loose aerial mycelium rather 

 than from submerged mycelium in the substratum. 



The cultural pictures of these species are fairly characteristic. Yet, it is 

 practically impossible to take a large collection of 100 or more strains and 

 separate them into these species with any degree of confidence or satisfac- 

 tion. The difference between A. oryzae and A. flavus is bridged completely 

 by a series of intermediate forms showing all degrees of variation between 

 the two strains selected as typical. Xomenclature in this group is then 

 further complicated by the fact that among the great collections of these 

 forms obtained from the Orient, and designated A. oryzae, the majority of 

 forms are somewhat intermediate between A. oryzae and A. flavus as de- 

 picted above. A similar series of intermediate forms bridges completely 

 the gap between A. flavus and A. parasiticus. There is no sharp line of 

 demarcation between any of these species, still they are not one and the 

 same, and to attempt to lump these diverse forms together into one species, 

 as Xeill (1939) has done for the ^4. glaucus group, intensifies rather than 

 reduces the difficulties encountered. 



Intra-group variation is also particularly marked in the .4. niger group. 

 During an extended period of study and observation of molds in culture, 

 Biourge, who was a discriminating collector, accumulated 63 strains of 

 black Aspergilli which suggested sufficient individuality to be deemed 

 worthy of further study. These were turned over to Mosseray when he 

 entered Biourge 's laboratory. He assumed that he had before him all of 

 the black Aspergilli possible to collect and, knowing that Biourge had 

 selected each of them because it seemed to have some special character, he 

 undertook a taxonomic study to define those characters and to organize 

 them into a systematic presentation (1934a). His paper lists 35 species of 



