USE OF THE MANUAL 111 



abandoned this practice since no satisfactory line of separation could be 

 found which differentiated between the truly monoverticillate forms and 

 the simpler of the biverticillate types. 



Asymmetrica: Conidial structures are characteristically once- or twice- 

 branched below the level of the sterigmata and are typically asymmetri- 

 cal (fig. 9). The metulae, cellular elements bearing the sterigmata, 

 occur in verticils terminating the main conidiophore only, or the main co- 

 nidiophore axis and one or more branches arising from it at the next lower 

 node. This section embraces the larger portion of the genus Penicillium, 

 hence has to be subdivided into sub-sections upon other characteristics. 

 Intergradation between this section and the Monoverticillata seem to 

 occur through at least two series of species, whereas other species appear 

 to be transitional between this section and the Biverticillata-Sym- 

 metrica. 



Biverticillata-Symmetrica : Conidial structures typically consist of 

 single terminal verticils of metulae, each bearing crowded verticils of 

 sterigmata that are characteristically lanceolate in pattern with acumi- 

 nate conidium-bearing tips (fig. 10). The over-all appearance of the 

 typical penicillus gives the impression of a fairly compact and completely 

 symmetrical brush or broom. Fractional penicilli are produced, in cer- 

 tain species, but even here the characteristic pattern of the cellular ele- 

 ments, particularly the sterigmata, is preserved. Species assignable to 

 this section quite commonly produce abundant yellow pigmented hj'phae 

 and oftentimes produce a strong pigmentation in the colony reverse and 

 agar which ranges from yellow through deep orange to bright red. Weh- 

 mer (1914) proposed the name Verticillatae for this section of the genus; 

 Biourge (1923) designated it as a sub-genus BiverticUlium; whereas Thom 

 first discussed it as the Penicillium luteum-purpurogenum group in 1915 

 and subsequently (1930) adopted the name used here. 



PoLYVERTiciLLATA : Thom (1930) created this section to include certain 

 species described by Bainier (1906 and 1907) which are characterized by 

 penicilli that are usually sjTnmetrical and which are branched at several 

 levels below the sterigmata. Conidiophores are regularly short and 

 heavy, and the cellular elements in the branching system are likewise 

 typically short and comparatively thick (fig. 168). IMembers of the 

 section are seldom encountered in culture. Type material has not been 

 available for study and the true relationship of these forms is not kno\\-n. 

 Their assignment here is dictated solely by the development of much 

 branched penicillate conidial structures. Other forms, more or less simi- 

 larly branched, have apparently been assigned to Scopulariopsis. 



"Related Genera": Certain forms develop penicillate conidial structures but 

 differ from Penicillium, in the generally accepted sense, sufficiently to 



