650 A MANUAL OF THE PENICILLIA 



conidiophores longer than on Czapek, mostly lOO/ii long; penicilli as de- 

 scribed above but showing conidial chains up to 150m in length. 



The species is distinguished particularly by its restricted growth and its 

 strongly elliptical, rugulose spores. Species description centered upon the 

 type culture, NRRL 1045 (Thorn No. 46) ; NRRL 1047 from the Biourge 

 Collection in 1924; and numerous others examined during this and earlier 

 work. The species is approximated by NRRL 1157 received in 1936 from 

 Dr. G. A. Ledingham, Ottawa, Canada, as an isolate from chickens in cold 



storage. 



Penicillium rugvlosum appears to be abundant in soil and in soil con- 

 taminated products and to be widely distributed. Cultures as newly iso- 

 lated usually produce abundant conidial structures upon all common sub- 

 strata, including Czapek's agar. When long maintained in culture, they 

 often tend to sporulate less heavily and to develop deeper mycelial felts. 

 The members of the species show a marked tendency to vary, and even in 

 normal cultures the irregular coloration of the colony in reverse may indi- 

 cate a degree of strain instability. 



The following species, subsequently described by other investigators, 

 are regarded as synonymous wdth Penicillium rugulosum Thom: 



Penicillium crateriforme Gilman and Abbott (Iowa State College Jour. Sci. 1: 293, 

 fig. 28. 1927) was assigned to the P. rvgidosim series by Thom (1930, p. 475). Re- 

 examination of Gilman and Abbott's type, now maintained as NRRL 1057, confirms 

 Thom's placement but fails to show sufficient differences to warrant species recogni- 

 tion. Colonies on Czapek are almost indistinguishable from those of NRRL 1045, 

 the type of P. rugulosum Thom, and differ from the latter on steep and malt agars 

 only in producing slightly faster-growing colonies and conidial areas in darker and 

 less yellowed shades. Conidia are strongly elliptical and rugulose. The culture is 

 regarded as representing a variation within the species P. rugulosum Thom. 



Two strains received from the Centraalbureau under this name in February 1946, 

 develop an intense red pigmentation on Czapek and steep agars, have smooth conidia 

 and produce broadly spreading and heavily sporing colonies on malt with a pro- 

 nounced apple to walnut odor. They are regarded as more nearly representing Peni- 

 cillium rubrum. Stoll in the P. purpurogemun series. 



Penicilliuyn cknjsitis Biourge (Monogr., La Cellule 33: fasc. 1, p. 252, Col. PI. XI 

 and PI. XIX, fig. 112. 1923) from Biourge's description and his culture (now NRRL 

 1053), supplied to Thom in 1924, is closely related to P. rugulosum Thom, but shows 

 slightly lighter colors in reverse. Recognition of this species would be warranted 

 only if the strains which we have included under P. rugjilosum were to receive names 

 enough to cover all of the quantitative differences in color production. 



Color Mutant: A tan-spored mutant, differing from the parent culture 

 only in the coloration of conidia, has been isolated from the type strain of 

 Penicillium rugulosum Thom, NRRL 1045. 



