600 A MANUAL OF THE PENICILLIA 



to 12 to 15. As in typical strains of P. avellaneum, metulae commonly arise not as a 

 true verticil at the tip of the conidiophore but over a considerable portion of the 

 terminal area; measurements of metulae, sterigmata, and conidia duplicate those of 

 P. avellaneum. Colonies spread broadly upon all media tested, sporulate abun- 

 dantly, and produce conidial areas in true avellaneous shades. We have observed 

 no evidence of an ascosporic phase. The type strain is maintained in our Collection 

 as NRRL 2110. 



Penicillium luteum Zukal, in Sitz.-Ber. Akad. Wein. 98: 561. 1889; Thorn, 

 U. S. Dept. Agr., Bur. Anim. Ind., Bui. 118, pp. 39 42, fig. 8. 1910; 

 Thorn, The Penicillia, pp. 448-449. 1930; Emmons, Mycologia 27: 141- 

 143, figs. 10 and 16. 1935. 



Colonies on Czapek's solution agar growng rather restrictedly, attaining 

 a diameter of 2.5 to 3.5 cm. in 2 weeks, consisting of a comparatively thin, 

 tough mycelial felt wdth surface appearing slightly fibrous, azonate or 

 slightly zonate, strongly wrinkled and buckled (fig. 155A), sometimes split- 

 ting, at first colorless to yellowish but soon developing orange-red shades 

 and often showing superficial tufts of bright yellow hyphae, often develop- 

 ing few perithecia or conidial structures (see malt agar) ; exudate lacking or 

 very limited; odor evident, sweetish; reverse in bright orange-red shades. 



Colonies on steep agar growing somewhat more rapidly than on Czapek, 

 more highly colored, and commonly developing bright yellow-green shades 

 from pigmentation of superficial hyphae, often not associated with conidial 

 structures; small, fractional penicilli sometimes produced in limited num- 

 bers; perithecia lacking. 



Colonies on malt extract agar very restricted (fig. 155B), about 1.5 to 

 2.0 cm. in 2 weeks, raised, 1 mm. deep, comparatively tough, commonly 

 consisting of an interwoven mycelial felt bearing a continuous surface layer 

 of massed perithecia and enveloping sterile hyphae, bright yellow in color, 

 near lemon yellow to lemon chrome (Ridgway, PL IV) ; conidial structures 

 often lacking or few in number, sometimes abundantly produced throughout 

 the entire growth or in localized areas and sectors, sometimes dominating 

 the colony appearance, in yellow-green, near pea green shades (R., PI. 

 XLVII); penicilli extremely variable, ranging from irregular aggregates of 

 few sterigmatic cells to biverticillate structures that are often irregularly 

 branched, occasionally almost symmetrical; metulae often lacking or diffi- 

 cultly identified; sterigmata variable in origin and dimensions, ranging 

 from 8 to 12/i or even 15^ in length by 2.5 to 3.0^ but consistently tapered 

 in the manner characteristic of the group; conidia elliptical to ovate, mostly 

 2.5 to 3.0/i by 1.5 to 2.0m; odor as on Czapek; reverse in dull brown shades; 

 perithecia variable in form and dimensions, often confluent, when borne 

 separately appearing rounded, oblong, or elongate, mostly 200 to 350m in 

 diameter, bounded by loose mycehal networks but without definite walls, 



