352 A MANUAL OF THE PENICILLIA 



types of military equipment in Panama, Florida, and the southwest Pacific 

 area. ■ The species appears to be widely distributed. 



No authentic cultures of Penicillium steckii Zaleski have been available 

 for the present study. Thom's culture No. 5010.22, cited as Zaleski's type 

 and discussed in Thom's Monograph (1930, p. 256), was lost from his Col- 

 lection some years ago. Presumably it is not available from the Centraal- 

 bureau, since it was not included among the Penicillia received from them 

 in 1946. Nevertheless, from Zaleski's original diagnosis and figures, and 

 from Thom's subsequent observations on Zaleski's culture, as reported in 

 the latter's Monograph, we believe that P. steckii must have represented a 

 form approximating the strains cited above. As understood by us, this 

 species differs from P. citrinum Thom primarily in producing colonies with 

 exudate and reverse less highly pigmented, penicilli equally divaricate but 

 somewhat less uniform in pattern, colonies more rapidly growing on malt 

 agar, and an inability to produce the antibiotic citrinin. 



Occasional strains are encountered which seem to differ from the above 

 only in their failure to produce well-defined columns of conidia. While 

 identification of such strains may prove somewhat troublesome due to the 

 construction of the key, they are believed to be closely related, hence are 

 assigned to the species Penicillium. steckii Zaleski as a variant. NRRL 

 2142, received from Professor Weston as an isolate from exposed fabric in 

 Panama, is representative of such forms. 



Occurrence and Significance 



Members of the Penicillium citrinum. series occur upon a wide variety 

 of substrata subject to soil or dust borne contamination including cotton 

 and other fabrics, dairy and food products, tobacco, leather goods, and 

 various vegetable materials undergoing slow decomposition. They occur 

 regularly in soil. They were encountered more frequently than any other 

 Penicillia among the molds isolated from deteriorating military equipment 

 in tropical and sub-tropical areas. They appear to be especially adapted 

 to growth upon leather and woven fabrics under field conditions where such 

 substrata would show great variability in water content. Members of the 

 series are not active cellulose decomposers, nor are they kno^\^l to rapidly 

 destroy nitrogen rich materials. Their role in decomposition processes, 

 if it is substantial, probably resides in their ability to gain an early foothold 

 and so prepare the way for the invasion of more destructive forms. Not 

 infrequently they occurred upon lens mountings, with the hyphae extending 

 out upon the glass surface and etching it sufficiently to render it unservice- 

 able. 



