566 A MANUAL OF THE PENICILLIA 



works of interlacing hyphae that remain essentially unmodified. In some 

 species, such as P. spiculisporum Lehman, P. bacillosporum Swift, and 

 P. duponti Griffon and Maublanc emend. Emerson, this covering may be 

 rather closely knit and at times simulate a true perithecial wall, while in 

 other species, such as P. wortmanni Klocker and P. liiteum Zukal, it may be 

 very thin and hardly apparent. The perithecium seems to arise in a num- 

 ber of different ways among the several species that comprise the series 

 (see below), but in all cases the course of development and the ultimate 

 structure of the mature body appears to be approximately the same. Peri- 

 thecial initials give rise to an enlarging mass of ascogenous elements which 

 becomes enmeshed in, and is surrounded by a supporting and protective 

 netw^ork of sterile and possibly nutritive hyphae. In most species the asci 

 begin to appear quite early, often within 4 to 6 days. According to Em- 

 mons (1935), the fertile region may subsequently increase in size materially 

 as a result of continued peripheral growth. On the other hand it may arise 

 from more than one center of origin. In no case is a firm, brittle, or sclero- 

 tioid structure produced. 



Asci are abundantly produced in most forms, and may be borne either 

 in short chains or singly as lateral buds from successive cellular elements 

 of the fertile hyphae. Emmons attached considerable importance to this 

 difference, a view with which we concur. It is believed significant that in 

 our key to the series (see p. 561), which is based upon other primary char- 

 acters, the species that produce asci in chains fall into one general sub- 

 series, while those that produce asci singly as lateral buds fall into another 

 sub-series. 



Ascospore patterns and markings differ substantially within the series, 

 and the differences exhibited are believed to provide a clue to natural 

 relationships, since cultural characteristics and certain other details of 

 structure can generally be correlated with them. 



To be consistent with our general practice of adopting for a series the 

 name of the species most representative of it, or the species most com- 

 monly encountered, we should refer to this as either the Penicillium wort- 

 manni or the P. vermiculatum series rather than as the P. luteum series. 

 However, this practice is not followed in the present case for the following 

 reasons: (1) the name P. luteum is the oldest name applied to an ascosporic 

 member of this section of the genus; (2) the name P. luteum is beautifully 

 descriptive of the cultural aspect of the yellow ascosporic phase of most 

 of the species comprising the series, and (3) the name has been widely 

 adopted in the literature to include yellow pigmented Penicillia producing 

 perithecia and ascospores. 



The Penicillium luteum series, as presented here, is believed to represent 

 a true natural series despite marked differences in ascospore patterns and 



