BIVERTICILLATA-SYMMETRICA 559 



often show abundant yellow encrusted vegetative hyphae, yet fail to pro- 

 duce sterigmata of characteristic pattern and develop a 3'ellow to bright 

 green or dark green rather than yellow to red pigmentation in the colony 

 surface and reverse with Czapek's agar. 



Certain species such as PenicilUum vermiculatum Dangeard, P. wortmani 

 Klocker, etc. that are consistently perithecial, develop conidial structures 

 entirely typical of the section (fig. 143B) and hence are included. Usually 

 these develop yellow or orange rather than red pigmentation in areas of 

 heavy mycelial development and in the colony reverse. Other perithecial 

 forms, obviously closely related, e.g., P. stipifatum Thom, tend to produce 

 fractional penicilli but show sterigmata (fig. 143A) and yellow encrusted 

 hyphae characteristic of the group. Still another, P. aveUaneum Thom 

 and Turreson, produces large, coarse penicilli hardly suggestive of the 

 section (fig. 143C), but develops perithecia and an abundance of yellow 

 encrusted mycelium strikingly like the above, hence is included here. 



The true relationships between perithecial and strictly conidial forms 

 are generallj'' obscure. Not infrequently, asexual strains have been ob- 

 served to originate in culture by a gradual and progressive reduction in 

 perithecium formation. More often, however, members of the section are 

 strictly conidial when isolated, and we can only speculate regarding their 

 possible origin in nature and their possible identity as unisexual haplonts. 

 Attempts to develop perithecial forms by growing such asexual strains in 

 pairs have proved unsuccessful. Yet, they often resemble so closely the 

 conidial phase of known perithecial species that close relationship, if not 

 actual identity, may be presumed. 



The non-ascosporic members of the Biverticillata-Sj^mmetrica are sub- 

 divided into five series, primarily upon the bases of colony texture and 

 coloration, as shown in the accompanying key. These are centered around 

 P. duclauxi Delacroix, P. funicidosum Thom, P. purpuogenum Stoll, P. 

 rugulosum Thom, and P. herquei Bainier and Sartory, as the most abundant 

 and representative species in the different series. Identification to species 

 in this, as in other sections, is often diflRcult, but assignment to series is 

 usually readily accomplished. Fortunately, identification to series is suf- 

 ficiently accurate for many types of investigations. 



A few species produce sclerotia. In all cases these are fairly irregular 

 in pattern and dimensions and appear to be less highly organized than 

 those seen in the PenicilUum thomii, P. raistrickii, and P. gladioli series. 

 They consist of irregular masses of comparatively large polygonal cells 

 with walls somewhat thickened and dark-colored, usually in deep reddish 

 brown, brownish black, or greenish black shades. Unlike the sclerotia of 

 series in other sections which are produced upon the agar surface, these 

 are often partially embedded within the substratum. 



