BIVERTICILLATA-SYMMETRICA 567 



dimensions, in origin and arrangement of asci, in the form and complexity 

 of perithecial initials, and in the overall coloration of growing colonies. 

 Such differences are regarded as being outweighed by essential similarities 

 existing between the perithecia produced and in the character of conidial 

 structures, especially the sterigmatic cells. It is not possible in all cases 

 to establish with certainty the correct inter-relationship of the species that 

 comprise the P. luteum series, and a number of divergent lines of develop- 

 ment are clearly apparent. These are discussed below. 



Penicillium duponti was originally described by Griffon and Maublanc 

 (1911) as a conidial species only. Thom (1930) placed it in his Asym- 

 metrica-A^elutina adjacent to P. oxalicum largely upon the pattern of its 

 penicilli and the elliptical character of its conidia. He called attention to 

 its thermophilic character. Recently, Professor Ralph Emerson has iso- 

 lated from retting guayule shrub (45-47°C.) at Salinas, California, strains 

 which duplicate almost exactly Griffon and Maublanc's description, but in 

 addition produce soft perithecia of the general pattern developed in the 

 P. luteum series. Furthermore, careful re-examination of the conidial ap- 

 paratus shows this to be often irregular and asymmetric but typically biver- 

 ticillate and sometimes symmetrical, and to bear lanceolate or acuminate 

 sterigmata that are likewise typical of the P. luteum series. The species is, 

 therefore, placed adjacent to P. stipitatum largel}^ upon the common char- 

 acter of ascospores with equatorial furrows and ridges. Perithecial initials 

 have not been observed in P. duponfi. 



Penicillium, stipitatum Thom, as described by Emmons (1935) and as 

 observed in our own cultures, produces ascospores and perithecial initials 

 of unique pattern. The ascospores are lenticular rather than elliptical 

 and show two prominent equatorial bands, often so closely appressed as to 

 appear as a single ridge (fig. 147D). The presence of a definite equatorial 

 zone with prominent ridges is strongly suggestive of the ascospores seen in 

 some members of the P. javanicum and Carpenteles series. Reasonably 

 close relationship to these series might be suspected were it not for other 

 structural and cultural differences, and for the fact that the same type of 

 ascospore is regularly seen in ascosporic species of Aspergillus. The struc- 

 ture of its perithecia, the pattern of its conidial apparatus, and the colora- 

 tion of colonies upon many substrata unmistakably ally P. stipitatum with 

 the P. luteum series. Perithecial initials are likewise unique as described 

 and illustrated by Emmons (1935). In no other species have we observed 

 a basal coil from which develops an elongate hypha that proliferates at its 

 terminus to give rise to a perithecium (fig. 144A). Asci are produced in 

 chains, a character that is shared by the majority of species assigned to the 

 P. luteum series. 



Penicillium vermiculatum Dangeard, P. wortmanni Klocker, P. helicum 



