BIVERTICILLATA-SYMMETRICA 573 



sporiim Lehman, P. hacillosponim Swift, P. stipiiatum Thorn, and P. luteum 

 Zukal to be homothalhc. Prior to this, and working with a different strain 

 of P. luteum, Derx (1925, 1926) had reported this species to be hetero- 

 thalhc and presented tabular evidence of paired monospore cultures in 

 support of his view. Emmons accepted Derx's resuUs as evidence of cul- 

 tural variation within his stock strain rather than as proof of heterothalhsm. 

 Irrespective of their origin, which is a matter that requires much additional 

 careful study, these sterile variants commonly develop in culture and being 

 of known lineage, are retained in the P. luteum series. This immediately 

 raises the question of the proper assignment of newly isolated strains which 

 show considerable evidence of relationship to the above but never show any 

 evidence of sexuality. In his Monograph, Thom (1930) referred to these 

 as belonging to the "P. luteum series, nonascosporic." The accuracy of 

 such an assignment probably cannot be improved upon. However, we 

 believe it less confusing taxonomically to consider such forms solely upon 

 the basis of their conidial structures and colony characteristics, and such a 

 course is followed in the present work. They are assigned to such pre- 

 dominately yellow-green species as P. variabile and P. verruculosum in the 

 P. purpurogeiium and P. funiculosum series, respectively. 



Many investigators have noted similarities between the perithecia of 

 Penicillium luteum and those of the genus Gymnoascus. As early as 1895 

 Saccardo (Sylloge XI: 437-438) transferred Zukal's species to Gymnoascus 

 upon bibliographic considerations. Thom (1930) considered this place- 

 ment, but concluded that many other characters indicating relationship 

 with true Penicilha outweighed it, and kept the species in Penicillium where 

 Zukal had originally placed it. Dodge (1933) and Emmons (1935) hke- 

 wise recognized close similarities between certain members of the series, 

 particularly P. wortmanni, and Gymnoascus but like Thom left them in 

 Penicillium. Continued study of the forms now in our possession, together 

 with the examination of additional isolates, may in time enable us to clarify 

 the true relationship of these two genera. For the present, however, we 

 believe that the user of this Manual will benefit if we consider together in 

 one genus all of the molds which produce true penicillate conidial structures, 

 irrespective of the structure of their perithecia. 



Penicillium duponti Griffon and Maublanc emend. Emerson, published here. 

 P. duponti Griffon and Maublanc, in Bui. Soc. Myc. France 27: 68-74, 

 figs. 4-8. 1911, represented the conidial stage only. 



This species is unique among the Penicillia in being strongly thermophilic, 

 growing at temperatures between 25° and 60°C., with an optimum at 45° 

 to^50°C. The species is known only from the original description based 

 upon two isolates, and from additional strains isolated by Professor Ralph 



