160 A ]VL\NUAL OF THE PENICILLIA 



received in 193G from Professor Westerdijk as a culture of this species 

 contributed by Stapp and Bortels (Berlin), as a soil isolate; NRRL 1640, 

 contributed by D. H. Linder, Xatick, Massachusetts, as an air contami- 

 nant; NRRL 2077, from Wm. H. Weston in June 1945, as an isolate from 

 a pine cone ; and numerous other strains examined during the course of our 

 investigations over a period of many years. 



The species is abundant and cosmopolitan in distribution. It is espe- 

 cially common in soil and has been repeatedly obtained from lumber and 

 other wood products. When first isolated, strains almost invariably pro- 

 duce abundant pink sclerotia, but with continued laboratory cultivation 

 tend to become increasingly conidial. Strains long maintained in collec- 

 tions often completely lose their ability to produce these characteristic 

 structures. Members of the species are subject to considerable variation 

 in culture, and the same colonies may contain sectors that are either pre- 

 dominantly conidial or sclerotial. In addition to variation in the relative 

 abundance of sclerotia and conidial structures, occasional strains show 

 sclerotia less definitely pink in color, and produce smaller conidial struc- 

 tures as short branches from interwoven aerial hyphae. This development 

 is suggestive of the PenicilUum decumbens series, although sclerotia have 

 not been reported for any of the species that comprise that series. 



Unlike PenicilUum sderotiorum where sclerotia are borne in clusters 

 within envelopes of brightly colored sterile hyphae, the sclerotia of P. ihomii 

 are borne singly and are naked or nearly so. The conidial apparatus of the 

 two species are strikingly similar. 



In 1910 (p. 78), Thom published descriptive notes on a culture. No. 29, 

 but did not assign to it a specific name. Maire published his description 

 of PenicilUum ihomii in 1917 and noted slight differences between his cul- 

 ture and Thom's No. 29. The differences, however, were minor in char- 

 acter and there was little question that the two investigators were dealing 

 with strain differences in two members of the same species. Accordingly, 

 Thom, in 1930, regarded his No. 29 (then lost from his collection) as repre- 

 sentative of Maira's species. Since that time the species concept has been 

 further broadened and today we tend to regard as representative of P. 

 ihomii Maire all monoverticillate strains producing hard, brittle sclerotia 

 that are pink in color. 



PenicilUum scleroiiorum van Beyma, in Zentbl. f. Bakt. etc., (II) 96: 



416-419, figs. 1 and 2. 1937. 



Colonies on Czapek's solution agar growing somewhat restrictedly, at- 

 taining a diameter of 2.0 to 3.5 cm. in 10 to 12 days at room temperature, 

 variable in color and texture depending upon the relative abundance of 

 sclerotia, vegetative hyphae, and conidial structures; varying from essen- 



