440 A MANUAL OF THE PENICILLIA 



10.0 to 12.0/x by S.Om; conidia elliptical to subglobose, mostly 4.0 to S.O/i 

 in long axis, smooth-walled. 



Colonies on steep agar essentially duplicating those on Czapek in rate 

 of growth and in general colony texture, but showing more numerous and 

 conspicuously radial furrows; exudate production and odor as described 

 above; colony reverse uncolored to light buff; penicilli as on Czapek. 



Colonies on malt extract agar duplicating the above in rate of growth, 

 but differing in texture, comparatively thin, plane, zonate, almost velvety, 

 with margins thin, largely submerged (fig. 114D); exudate lacking; odor 

 spicy; reverse uncolored or becoming yellowish in age; penicilli as above. 



Species description based upon the type strain, NRRL 890 (Thom's 

 No. 23), which was isolated by Thom from cheese in 1904 at Storrs, Con- 

 necticut. The culture has been under continuous laboratory cultivation 

 since that time without significant change in cultural or morphological 

 characteristics. NRRL 891, which represents the same strain sent to 

 Biourge and returned to us, produces thinner, more restricted, and lighter 

 sporing colonies but still retains the basic species characters. Three cul- 

 tures were received from the Centraalbureau as Penicillium commune 

 Thom in February 1946. One of these, labeled "Thom I", and in corre- 

 spondence indicated to be Thom's No. 23, no longer presents the typical 

 cultural picture of the species. Colonies are relatively close-textured and 

 produce comparatively few and small conidial structures; but spore di- 

 mensions remain satisfactory. It is probable that the strain returned to 

 us represents a cultural variant which has developed during the period of 

 laboratory cultivation in Baarn. A second culture, labeled "Thom II" 

 represents Thom's strain 4733.40 as received from Biourge. Culturally 

 it is similar to NRRL 890 but produces more restricted, more strongly 

 furrowed and more heavily sporing colonies. A third culture, labeled 

 "from Cichorium intyhus, 1944" essentially duplicates the preceding but 

 shows conidial areas in somewhat brighter blue-green shades. 



When first described, Thom believed this species to be unusually com- 

 mon in nature, hence the name. Continued study of the genus Penicillium 

 has failed to substantiate this belief, and P. commune today must be re- 

 garded as a rather unique species which is only occasionally encountered. 

 Once recognized, the experienced mycologist should encounter little diflii- 

 .culty in subsequently identifying the species. 



Culturally and microscopically Penicillium commune bears a striking 

 resemblance to P. puhcrlum Bainier as that species is known from Alsberg 

 and Black's strain, now maintained as NRRL 845. Colonies of NRRL 

 890 are generally somewhat deeper and of looser-texture, but in general 

 habit and coloration often duplicate almost exactly those o^ NRRL 845. 



