ASYMMETRICA-VELUTINA 349 



mediate length arising from submerged hyphae. Penicilli variously 

 branched or monoverticillate, commonly appearing 2-parted, with terminal 

 and secondary branch equal or unequal in length; not infrequently con- 

 sisting of terminal verticils of 3 or 4 bi'anches (or metulae) approximately 

 equal in length and withal presenting the picture of typical P. cilrinum. 

 Represented by XRRL 783 (Thom 5048.14), received in 1929 from Pro- 

 fessor Lewis, University of Texas, and XRRL 784, received in 1931 from 

 Dr. H. C. Greene, University of Wisconsin. Thom described P. sartoryi 

 n. sp. (1930, p. 233) to cover the general morphology of such forms, em- 

 phasizing the branching habit of many of its conidiophores and the abun- 

 dance of monoverticillate penicilli. He assigned the species to his Mono- 

 verticillata-Ramigena and placed it at the end of that group adjacent to 

 the As3'mmetricaA^elutina. ^\Tien tested against selected bacteria in 

 spectrum plate tests, XRRL 783 and 784 were found to produce some 

 citrinin (Wickerham, unpul^lished notes). This additive evidence of 

 relationship, coupled with the fact that these forms differ from typical 

 P. cilrinum strains primarily in the production of more irregularly branched 

 and often simpler penicilli, leads us to consider them only as representative 

 of a group of variants within the abundant and cosmopolitan species P. ci- 

 trinum Thom. 



(5) Color mutants: Two striking color mutants have been encountered 

 in Penicillium citrinum Thom. The first of these, X'RRL 2145, was re- 

 ceived in July 1945 from Dr. Oswaldo G. de Lima, Recife, Brazil, and is 

 characterized by conidial areas in light tan shades approximating avellane- 

 ous to olive buff (R., PI. XL); colony texture, pattern, rate of growth, and 

 color in reverse are characteristic of the species; penicilli regularly consist 

 of 3 to 6 metulae bearing closely compacted sterigmata and conidial chains 

 in well-defined columns up to 75 or 100/z in length. Colonies on malt agar 

 are restricted and heavily sporing, hence characteristic of the species. 

 ^Vllen cultures are allowed to incubate at room temperature for 10 to 14 

 days and are then placed in a cold room there is some tendency to develop 

 green conidia — not as sectors but as a diffuse development throughout the 

 younger conidial areas. Except for the color of its conidia, this strain 

 seems to duplicate XRRL 2143 (see p. 348) in all particulars. It produces 

 a typical citrinin pattern when tested on bacterial spectrum plates. 



The second mutant first appeared as a white sector in a colony of XRRL 

 783 growing on steep agar. Isolated in pure culture, a substrain was 

 obtained which continued to produce colonies characteristic of the parent 

 culture except for a complete lack of conidial color. Structurally the mu- 

 tant duplicates the parent (see above). The capacity of the mutant to 

 produce citrinin is unimpaired. The mutant is maintained in our Collec- 

 tion ^s XRRL 783,A. 



