MONOVERTICILLATA 143 



very tardily (4 to 5 weeks) develop mature asci and ascospores in limited 

 numbers. 



Ripening of the ascocarp, or perithecium, apparently follows the course 

 reported by Dodge (1933). Perithecia were described as at first consisting 

 of "a solid mass of pseudoparenchymatous tissue with little or no differen- 

 tiation except for the somewhat thicker walls of the cells of the outer 

 layer." The ascogenous system occupied a central position and gradually 

 increased by disorganization of the surrounding tissue. In old perithecia 

 the entire body, with the exception of a comparatively thin outer wall, was 

 composed of mature asci. The fruit body was reported not to be hard and 

 stone-like at any stage although some structures more definitely sclerotioid 

 than most were encountered. In certain cultures, asci were visible in 

 7 days and ascospores were matured within 10 days after the cultures were 

 planted; in other cultures the process was more delayed. Ascospores were 

 reported as finely echinulate but no mention was made of an equatorial 

 band or furrow, nor was such shown in his illustrations. Ascospores germi- 

 nated usually by splitting, with the spore walls remaining in two fragments 

 as in definite bi-valve types. Emmons (1935) figured the ascospore with a 

 faint suggestion of an equatorial furrow. In our experience such a line or 

 furrow is sometimes evident although usually lacking. 



The conidial apparatus in NRRL 710 remains typical of the species. 

 The penicilli are typically monoverticillate but not infrequently show 

 branched structures as originally illustrated. Sterigmata consistently 

 show the narrow conidium-bearing tip described by Dodge. Conidia are 

 definitely elliptical and agree satisfactorily with his original measurements 

 (fig. 39C and D). 



Although the species was shown to be homothallic by both Dodge (1933) 

 and Emmons (1935), most strains of Penicillium hrefeldianum in continued 

 artificial culture show a marked tendency to develop sectors that are pre- 

 dominantly conidial. Even by exercising special care as to areas from 

 which recultivations are made, it is often extremely difficult to maintain a 

 strain which produces abundant and normally maturing perithecia. Strains 

 freshly isolated from nature generally produce quantities of perithecia, but 

 often lose this capacity in large measure after relatively few transfers. The 

 type, NRRL 710, is an example. Other strains maintained in this labora- 

 tory for more than a decade show no evidence of developing asci, although 

 there remains some suggestion of perithecial initials. A strain received 

 from the Centraalbureau in February 1946, as Carpenteles hrefeldianum 

 (Dodge) Shear, undoubtedly ascosporic when first isolated and diagnosed 

 by them, produces small rounded masses of heavy-walled cells but shows 

 no evidence of ascospore development. 



A number of strains believed to represent Penicillium hrefeldianum Dodge 



