340 A MANUAL OF THE PENICILLIA 



the range of which is indicated in the discussion of the species and indicated 

 in some degree in fig. 92. Some citrinin is almost invariably produced by 

 strains assignable to this species upon cultural and morphological grounds, 

 thus providing additional evidence of close relationship. The character- 

 istics of the species are, in general, those of the series as listed above. 



Penicillium steckii differs in showing less pigment both in colony reverse 

 and in its exudate, in developing dull yellow-green rather than blue-green 

 shades in conidial areas, in growing somewhat more rapidly upon most sub- 

 strata, and in its failure to produce citrinin. 



Penicillium corijlophilum produces thinner and usually closer-textured 

 colonies, with penicilli often smaller, less regular in pattern and showing 

 less well-defined columns of conidia. The species does not produce citrinin. 



The Penicillium citrinum series seems to be comprised of a group of 

 transitional species. Penicillium citrinum Thom appears to be interme- 

 diate between monoverticillate forms with ramigenous penicilli on the one 

 hand and members of the P. chrysogenum series on the other. Occa- 

 sional cultures are seen, such as that upon which Thom (1930) based his 

 species P. sartoryi (see p. 349), which shows the loose irregular branching 

 habit of certain monoverticillate species coupled with the general appear- 

 ance and coloration of typical P. citrinum. It is believed significant that 

 such cultures produce citrinin. On the other hand, occasional cultures are 

 encountered which culturally and structurally suggest P. notatum Westling, 

 and such strains by spectrum plate tests appear to produce both citrinin 

 and penicillm. 



Penicillium corylophilum Dierckx, as kno'wn to us by the type and other 

 representative strains, appears to be intermediate between such forms as 

 P. citrinum and members of the ramigenous series of the Monoverticillata. 

 Maximal conidial structures show the characteristic biverticillate pattern 

 of the present series, hence this placement. Oftentimes, however, an 

 equal number of penicilli appear monoverticillate, with such structures 

 variously and irregularly arranged. 



Penicillium steckii Zaleski, in the sense of this Manual, appears to be 

 transitional toward the Divaricata, particularly in the direction of P. jen- 

 seni Zaleski. Both species show reduced pigmentation, both produce 

 penicilli consisting of terminal verticils of metulae, whereas neither pro- 

 duces citrinin or any other laiown antibiotic. Penicillium steckii is like- 

 wise suggestive of the P. raistrickii series in the Divaricata, but differs from 

 the latter in its failure to develop sclerotia and in producing smooth rather 

 than rough-walled conidiophores. Finally, P. steckii is suggestive of P. 

 paxilli Bainier in the P. hrevi-compactum series, differing from that species 

 primarily in the smaller number and less crowded arrangement of its 

 metulae. 



