BIVERTICILLATA-SYMMETRICA 577 



guayiile shrub, removed and incubated at 45°C., May 1945; also guayule 

 shrub retted at controlled temperatures of 47 °C. in continuously rotating 

 drum and subsequently removed and incubated at 47°C., December 1945." 

 Emerson writes as follows regarding the species: 



"Penicillium duponti, like all the molds isolated from retting guayule, actively 

 decomposed guayule resins in resin-emulsion media; and, in pure culture rets, lowered 

 the resinous fraction of the crude rubber from IS per cent to 11 per cent. 



"Until the present isolate was obtained from guayule, Penicillium duponti had 

 apparently not been seen since its discovery by Griffon and Maublanc in 1911. Their 

 careful description fits the present strains with remarkable closeness. The species 

 still occupies a unique position, recognized by Griffon and Maublanc, as the only true 

 Penicillium wliich can be justly included in the small group of molds known to be 

 strongly thermophilic. 



"By germinating the ascospores and obtaining therefrom the typical conidial 

 stage of Penicillium duponti, the genetic relation between the sexual and asexual 

 phases was definitely established. The tests necessary to determine whether the 

 species is homo- or hetero-thallic have not yet been made. Nor are the factors under- 

 stood which stimulate the formation of perithecia. The particular prevalence of 

 perithecia in the lower layers of shrub in pure culture rets suggests that partial de- 

 ficiency of oxygen may play a role. This idea has been borne out to some extent in 

 experiments where perithecia were abundantly produced in agar cultures held under 

 reduced oxygen pressures, but carefully controlled studies will be required to clear 

 the matter up." 



Perithecia in Penicillium duponti, as described and photographed by 

 Emerson (fig. 146), commonly show a heavier peridium than other mem- 

 bers of the P. luteum series. These, however, differ mostly in thickness 

 rather than in basic structure. In P. stipitatum, the species next to be 

 considered, perithecial walls of closely interwoven hyphae approaching 

 those of P. duponti are often seen. 



Penicillium stipitatum Thom, Emmons, jMycologia 27: 138-141, figs. 6, 7, 



and 16. 1935. 



Emmons' description as follows: 



"Colonies on Czapek's solution agar floccose, tufted in yellow (luteus) shades pass- 

 ing over to orange or even red-orange shades in age; reverse yellow to red-orange; 

 aerial hyphae studded with granules yellow in the young and growing period becom- 

 ing reddish in age; conidial apparatus irregularly biverticillate with sterigmata up to 

 10 by 2n, taper pointed and closely packed in the verticil; conidia about 3.5m in long 

 axis, rather thick-walled fusiform smooth; ascogenous masses enveloped by tufts and 

 masses of yellow hyphae, within which hyphae are arranged into a fairly definite wall 

 forming a brittle and easily crushed perithecium; asci 8-spored, ripening quickly, 

 5.5-6.5 x 7-8m. 



"Ascospores 3-3.6^ in long axis by about 2)u, lens-shaped consisting of a two valved 

 body with an equatorial band or frill about 0.5m in width, usually appearing singly 

 but occasionally apparently double with a groove partially evident between them." 



