Plate I 

 Natura mutations in species of Penicillium 

 TOP: Penicillium notatum Westling, showing the normal parent strain, NRRL 832 (dark blue-green 

 colony), and a mutant, NRRL 832. A26, marked by the production of an abundant pink aerial mycelium. 

 Steep agar; 12 days. BOTTOM: Penicillium urticae Bainier, showing the normal parent strain, NRRL 2159 

 (light blue-green colony), and a mutant, NRRL 2159. A, characterized by colorless conidia. Czapek's solu- 

 tion agar; 12 days. (Color photographs by Haines, Northern Regional Research Laboratory. Reproduced 

 through co-operation of Chas. Pfizer & Co., Inc.) 



