VARIATION 



67 



would describe them as four distinct species. Actually, however, they are 

 not sufficiently distinct to warrant specific rank, for they represent only 

 extremes of variations along three divergent lines with numerous inter- 



Fig. 16. Intraspecies variation in Aspergillus terreus. A, A. terreus, typical 

 strain NRRL No. 265, characterized by heavy conidium production and colonies 

 cinnamon in color. B, A. terrreus var. boedijni, NRRL No. 680, characterized by 

 deeper colonies and conidial heads near xanthine yellow. C .A . terreus var. floccosus, 

 NRRL No. 1921, characterized by loose floccose colonies and spore heads light 

 pinkish-cinnamon in color. D, A. terreus var. aureus, NRRL No. 1923, character- 

 ized by yellow floccose colonies and comparatively few cream to buff-colored conidial 

 heads. 



grading strains aligning them, almost without interruption, with the typical 

 form itself. 



Another series of variants in our collection shows gradation from the 

 usual radiate head and conidiophore of A . sydowi to the simple mono-verti- 

 cillate penicilli of Penicillium restrictum Abbott. The tendency to form 



