134 A MANUAL OF THE PENICILLIA 



Later a knot of rather thick, irregularly wound or clumped hyphae, which 

 represents the beginning of the young ascocarp, or perithecium, appears in 

 •a fork of the branching system. Growth is rapid from this stage and the 

 young ascocarp soon consists of a solid mass of pseudoparenchymatous 

 tissue with little or no differentiation except for the somewhat thickened 

 walls of the cells of the outer layers. The ascogenous system apparently 

 occupies a central position. Depending upon the species and strain, and 

 upon the substratum and other environmental conditions as well, asci may 

 begin to appear within 7 to 10 days; or the whole mass may become sclero- 

 tioid and ascus formation be delayed for a matter of 3, 4, 5, or more weeks. 

 In some strains and under certain conditions the bodies appear to remain 

 sclerotioid indefinitely and cannot in fact be distinguished from true 

 sclerotia (fig. 13). In any case, wherever asci develop, these first occupy 

 a central position in the perithecium and arise as short branches from the 

 fertile ascogenous hyphae that comprise an enlarging network which grad- 

 ually disorganizes (digests ?) and replaces the pseudoparenchymatous tissue 

 (fig. 35). Generally speaking, and making certain allowances for some 

 species other than P. hrefeldianum, Dodge (1933, p. 97) was correct in say- 

 ing: "The older the ascocarp under good growing conditions the larger the 

 cavity and the greater the number of asci with a corresponding thinning 

 out of the sterile wall layers." In discussing the perithecia of P.javanicum, 

 the first described member of the series, van Beyma (1929) reported them 

 to ripen late (usually one month or more) and to consist of a tough pseudo- 

 parenchymatous cover, which when broken permitted the fertile hyphae 

 with budding asci to be "pressed out like a skein" (fig. 14E). This phe- 

 nomenon has been repeatedly observed in our experience. Whereas par- 

 ticular strains and species differ in the relative amounts of this hyphal net- 

 work and in the proportions of this network to the number of asci produced, 

 it is a characteristic developmental feature of this entire series, and also of 

 the Carpenfeles series, with biverticillate-asymmetric penicilli, which will 

 be considered later (pp. 260-273). 



Five species comprise the series as follows: Penicillmm javanicum van 

 Beyma, P. parviim Raper and Fennell, P. brefeldianum Dodge, P. ehrlichii 

 Klebahn, and P. levitum Raper and Fennell. For convenience, these species 

 may be subdivided into two fairly well defined sub-series. 



The first of these sub-series embraces Penicillium javanicum and P. par- 

 vum, and is characterized particularly by colonies that develop abundant 

 red to reddish brown pigmentation upon most substrata. Perithecia are 

 rather late in ripening in both species, particularly the latter, where asci 

 and ascospores commonly do not appear for several weeks. In P. parvum 

 colonies are much restricted and ascospores are usually small and show 

 conspicuous equatorial ridges (fig. 37). 



