168 A MANUAL OF THE PENICILLIA 



with surface growth consisting of trailing hyphae and ropes of hyphae, usually with 

 centre depressed or folded and wrinkled; reverse dark dull purple becoming very 

 deep brownish purple, with colour diffusing slightly into medium; drops colourless; 

 dense masses of compacted mycelium formed but no true sclerotia; colonies on wort 

 agar growing somewhat more rapidly than on Czapek agar, at first white, with patches 

 of grej'ish green, slightly floccose and funiculose, wrinkled and buckled, after a few 

 days developing masses of pale buff to pinkish brown sclerotia; reverse brownish; 

 conidiophores arising from trailing hyphae and ropes of hj^phae, mostly simple but 

 with an occasional branch, 35 to 55m by 1.5 to 2.0ju, smooth, slightly swollen at apex; 

 penicilli mostly strictly monoverticillate but occasionally, especially on Czapek 

 agar, with one or two sterigmata proliferating and developing single crosssepta (i.e. 

 with occasional metulae mixed with sterigmata) ; sterigmata almost cylindrical, 10 to 

 11 (15)At by 1.8 to 2.0m; conidia smooth, ovate at first, becoming globose to sub-glo- 

 bose, 2 to 2.5m diameter, or 2.3 to 2.8m by 2.0 to 2.2m; sclerotia brownish, irregularly 

 globose, averaging 300m in diameter, mostly confluent, composed of masses of irregu- 

 larly globose or polygonal cells." 



Isolated by Dr. G. E. Turfitt, Department of Biochemistry, London 

 School of Hygiene and Tropical Medicine, Universit}^ of London, from 

 samples of dried blue peas. Maintained in the L.S.H.T.M. Collection as 

 Catalogue Xo. 147 and so reported by Smith in his species diagnosis. 



In discussing Turfitt's culture, Smith called attention to its very re- 

 stricted growth on Czapek agar and to the curious dark dull purple reverse 

 of colonies on this substratum. Growth on wort agar was more rapid and 

 masses of sclerotia appeared after a few days. He compared the mold with 

 other monoverticillate Penicilha known to produce sclerotia and concluded 

 that it represented a new species, an opinion in which we concur. 



As a monoverticillate Penicillium producing sclerotia, PeniciUium pusil- 

 lum is properly assignable within or adjacent to the P. thomii series. The 

 species is suggestive of P. phoeniceum v. Beyma in the pigments developed 

 in the colony reverse upon Czapek agar and also in the restricted character 

 of its growth. In producing sclerotia upon wort agar but not upon Czapek, 

 the species is strongly suggestive of P. turhalum W3stling, wherein the same 

 condition prevails. The latter species, as originally described, and as ob- 

 served in our cultures, however, fails to develop any purple pigmentation. 

 Believing the production of sclerotia by a mold to be more fundamental 

 than the elaboration of similar colors, we are led to assign P. pusillum. with 

 P. turbatum rather than P. phoeniceum. The two species are regarded as 

 constituting a sub-series characterized by the production of sclerotia upon 

 some substrata but not on others, in contrast to the P. thomii series, in a 

 strict sense, whose member-species regularly produce sclerotia upon all 

 substrata. 



Occurrence and Significance 



Penicillium thomii Maire is widely distributed in nature. It is encoun- 

 tered in almost all soils examined, and commonly occurs on lumber and 



