112 A MANUAL OF THE PENICILLIA 



be excluded from that genus. Other genera which have been commonly 

 discussed as Penicillia include Gliodadium Corda (figs. 169 and 170), 

 Paecilomyces Bainier (fig. 171), and Scopulariopsis Bainier (fig. 172). 



The above separations are admittedly arbitrary, and intergrading forms 

 are found which bridge between the various sections as proposed. Specific 

 examples of transitional forms will be brought out in the discussions that 

 follow. 



Even though the most striking and the most stable characteristics avail- 

 able are employed for separation, forms of intermediate or uncertain rela- 

 tionships are regularly encountered and sharp lines often cannot be drawn 

 between the major sections or, for that matter, between sub-sections, series, 

 or even species. Successful taxonomy of the genus, therefore, must depend 

 upon the judgment of the worker as well as adherence to certain rules which 

 are too often rather indefinite when applied. 



A second basis of separation hinges upon whether or not perithecia or 

 sclerotia are produced. Perithecia characterize one series in each of the 

 three major sections. Perithecia are basically similar and a degree of close 

 relationship is indicated between the Penicillium javanicum series of the 

 Monoverticillata and the Carpenteles series of the Asymmetrica. The peri- 

 thecia developed by P. luteum and allied species of the Biverticillata-Sym- 

 metrica are, however, quite different from the above and potent arguments 

 have been advanced for taking these forms out of Penicillium and assigning 

 them to another genus such as Gymnoascus. This view might have merit 

 were it not for the fact that the conidial structures of ascosporic species are 

 often indistinguishable from those of other species in which perithecium 

 formation has not been observed. Further-more, it is not uncommon for 

 an ascosporic species to lose its capacity to produce perithecia, and there- 

 after to continue in culture as a conidial strain wholly typical of the Bi- 

 verticillata-Symmetrica section. 



The production of sclerotia approaches that of perithecia in its usefulness 

 as a diagnostic tool. Like perithecia, sclerotia are developed in widely 

 separated areas of the genus Penicillium. Unlike the situation in Asper- 

 gillus, their appearance does not seem to indicate close relationships of the 

 different series where they occur, or to separate the genus into major natural 

 divisions. 



A third basis of separation rests in colony characteristics — i.e., primarily 

 in the texture and pattern of the surface, or aerial growth. Sub-sections 

 and series are established upon the following bases: colonies are regarded as 

 velvety if conidial structures arise as a dense stand from a submerged my- 

 celium to produce a velvety effect (fig. 3A) ; colonies are regarded as lanose 

 if conidial structures arise from a loose or floccose aerial network to produce 

 a cottony, floccose, or lanose effect (fig. 3B) ; colonies are regarded as funicu- 



