BIVERTICILLATA-SYMMETRICA 569 



Raper and Fennell and P. rotundum of the same authors are believed to be 

 fairly closely related. All produce ascospores that are spinulose over their 

 entire surface and show no sign of an equatorial zone. Penicillium vermi- 

 cidatum is distinguished particularly by its long clavate to vermiform peri- 

 thecial initials as reported and illustrated by Dangeard (1910), and subse- 

 quently verified by Emmons (1935) . They are regarded as a distinguishing 

 characteristic in the present study (fig. 144B). While it has not been 

 possible for us to make cytological studies, superficial examination of 

 typical strains suggests a strong possibility that this species produces true 

 ascogonia and antheridia and that some type of sexual fusion may occur. 

 Emmons (1935) beheved an actual copulation took place but failed to ob- 

 serve such. Penicillium wortmanni in culture bears a striking resemblance 

 to the above, and its ascospores are practically indistinguishable from 

 those of P. vermiculaium. Perithecial initials, however, differ markedly. 

 There is no indication of differentiation into ascogonia and antheridia, the 

 first evidence of a developing perithecium being the appearance of swollen, 

 deeply staining, intercalary segments of aerial hyphae which become 

 broken up into short cells (fig. 144C) and may be more or less branched. 

 In P. rotundum much the same condition prevails (fig. 144F), but the clus- 

 ters of swollen cells are not limited to aerial vegetative hyphae and may 

 even appear in structures that are penicillate and which apparently started 

 out to develop as conidial structures. The production of globose spores 

 clearly separates it from P. wortmanni. In P. helicum the perithecial initial 

 first develops as a long, thickened, deeply staining hypha not markedly 

 different from that of P. vermiculatum. A thinner hypha, possibly an 

 antheridium, is almost invariably coiled around the base of the larger 

 hypha probably representing an ascogonium, and terminates as a sHghtly 

 flattened enlargement closely appressed against the wall of the latter. 

 Cytological studies have not been made and we have not succeeded in 

 determining whether any type of fusion occurs. In any case, at about 



Fig. 144. Initial stages of perithecium, or ascocarp, formation in members of the 

 Penicillium luteum series. A, P. stipitatimi Thom, NRRL 2105; note the coiled 

 hyphae at base, from which arises a heavy club-like structure that proliferates at its 

 terminus to produce the young ascocarp, X 375. B, P. vermiculatum Dangeard, 

 NRRL 2098; note the heavy clavate to vermiform hypha (presumably the ascogo- 

 nium) around which a smaller hypha (possibly the antheridium) is tightly coiled, 

 X 375. C, P. wortmanni Klocker, NRRL 1017, first evidence of perithecial origin 

 consists of irregular knots of enlarged hyphae as shown, giving no clue to identity of 

 possible ascogonia and antheridia, X 800. D, P. helicum Raper and Fennell, NRRL 

 2106; a long thick non-septate hypha (ascognium?) first appears, which subsequently 

 contracts into a spring-like coil— meanwhile a smaller hypha becomes tightly coiled 

 around the basal portion of the large hypha, X 375. E, P. spiculisporum Lehman, 

 NRRL 1026; initial stage appears as a heavy, irregular and usually knotted body as 

 shown, X 800. F, P. rotundum Raper and Fennell, NRRL 2107; initials are most 

 irregular in pattern and may even start as penicillate structures— the developmejit 

 shown is representative, but duplication of pattern need not be anticipated, X 675. 



