BIVERTICILLATA-SYMMETRICA 571 



mycelium; more closely interlaced hyphal networks surroundino; its peri- 

 thecia; and the common occurrence of monoverticillate penicilli. 



Penicillium luteum Zukal is the oldest of the recognized members of the 

 series and is at the same time one of the least well known species. This 

 results from the infrequent isolation of Zukal's form, and from the con- 

 fusion attendant to the assignment of various other ascosporic forms to this 

 species by later investigators. Our diagnosis of the species is based upon 

 the strain used by Emmons (1935) in his study of ascocarps in Penicillium, 

 and we have every reason to believe that it is representative of Zukal's 

 original isolate. The perithecia are unusually loose-textured, as in P. 

 wortmanni, and are accompanied by the development of abundant en- 

 crusted hyphae of bright yellow color which give to the culture upon most 

 substrata a coloration that is truly "luteus." Penicilli are often fractional 

 but are otherwise wholly characteristic of the series. Perithecial initials 

 are in the form of two short coiled hyphae as reported and illustrated by 

 Emmons (1935). Ascospores are unique and diagnostic of the species, 

 and may be characterized as follows: broadly elliptical, with walls smooth 

 or nearly so except for a spiral band or bands of raised protuberances or 

 echinulations which, under the microscope and in any single plane, appear 

 transverse (or tricostate, fide Zukal). Asci are not borne in chains as in 

 all of the above species, but develop as lateral buds from fertile hyphae 

 as in members of the P. javanicum and some members of the Carpenteles 

 series. A degree of relationship to these forms may thus be indicated. 



Penicillium avellaneum Thom and Turesson is usually separated from 

 other members of the series upon the basis of its tan to light brown (avel- 

 laneous) conidia. In addition to this character the conidial apparatus it- 

 self is somewhat unique. Although often appearing symmetrically biver- 

 ticillate it typically consists of a larger number of crowded metulae, and 

 withal produces an unusually large and compact penicillus (fig. 143C). 

 Metulae are generally heavier than in most species and the sterigmata 

 usually fail to show the characteristic lanceolate pattern of the Biverti- 

 cillata-Symmetrica section. Despite these differences, the species is re- 

 garded as properly assigned here. Perithecia are regularly accompanied 

 by the production of mantles of coarse, encrusted, yellow hyphae and show 

 the basic structure characteristic of other members of the series. Usually 

 accompanying the development of perithecia, and sometimes in their ab- 

 sence, are coarse hyphae with walls in purple or purple-red shades which 

 when massed lend to the colony a marked purple pigmentation in surface 

 and reverse. Thom and Turesson (1915) figured the perithecium as bounded 

 by a single layer of specialized, flattened, and thick- walled cells. Careful 

 examination of different strains in the present study has failed to show such 



