54 A MANUAL OF THE PENICILLIA 



the sclerotia are elongate and consist of a compact mass of dark, thick- 

 walled cells. In contrast to the sclerotia already described which are 

 borne upon the agar surface, those of P. novae-zeelandiae are as a rule 

 wholly or partially buried within the substratum (fig. 167). Sclerotia of 

 the same general type are occasionally encountered in strains of P. funi- 

 culosum and are characteristic of Thom's P. purpurogenum var. ruhri- 

 sderotium. 



PERITHECIA 



Perithecia regularly occur in three separate series, one of which occurs in 

 each of the three major sections of the genus Penicillium. The presence 

 of perithecia, therefore, while it constitutes our best basis for diagnosis and 

 separation of individual strains and species, cannot be considered as 

 characteristic of any major part of the genus and not of others. In general, 

 two markedly different types of perithecia are produced. 



In the Carpenteles series, and to a greater or less degree in the Penicillium 

 javanicum series, the perithecia first develop as masses of thick-walled 

 cells strongly suggestive of sclerotia (fig. 14). These subsequently produce 

 ascospores by a process of differentiation and maturation which begins 

 first at the center of the body and gradually progresses outward. In some 

 cases ripe ascospores may appear within a week to ten days. In others, 

 the development of such ripe spores may require a month or more. The 

 general type of perithecium found here was described in considerable, 

 detail by Brefeld in his study of "P. glaucum" in 1874. Half a century 

 later, in his study and description of P. hrefeldianum, Dodge (1933) dis- 

 cussed the origin and development of a perithecium of the same general 

 type and considered at length the formation and ripening of asci and 

 ascospores. The subject was further elaborated by Emmons (1935) in 

 his study of ascocarp formation in the genus Penicillium. The reader is 

 referred to these original papers and to our general discussions at the be- 

 ginning of the P. javanicum and Carpenteles series, respectively. 



In the Penicillium luteum series the perithecium develops in an entirely 

 different manner (fig. 15). A loose network of specialized hyphae develops 

 which may or may not be surrounded by a protective covering or peridium. 

 If such a covering appears, it usually consists of a loose network of inter- 

 lacing, highly pigmented hyphae usually bright yellow in color. In a few 

 cases these may become sufficiently compacted together to form a mem- 

 branous sheath or envelope. Emmons (1935) reported and illustrated the 

 type of perithecial initials present in the species examined by him (fig. 16). 

 In the present study we have confirmed his observations, almost without 

 exception, and have included observations on some additional new species. 

 Great variability is shown (see fig. 144), and some question exists as to 



! 



