648 A MANUAL OF THE PENICILLIA 



other cases the deficiencies may be identified, but the organisms still retain 

 distinctive characteristics even after the deficiency has been removed. 

 The description of a neW species is then necessary. Such was the case with 

 P. diversum Raper and Fennell. Extremely limited growth on Czapek and 

 steep agars could be attributed to an inability to utilize nitrate nitrogen, since 

 strains of this species grew normally when ammonium rather than nitrate 

 compounds were supplied as a nitrogen source. A variety of P. diversum, 

 P. diversum var. aureum was recognized by these authors to include occa- 

 sional strains which exhibited the same basic characteristics but on some 

 substrata showed a luxuriant development of sterile yellow aerial myce- 

 lium which effectively distinguished them. 



Penicillium rugulosum Thom, in U. S. Dept. Agr., Bur. Anim. Ind., Bui. 



118, pp. 60-61, fig. 21. 1910; The PeniciUia, pp. 472- 



474, figs. 80 and 81. 1930. 



Colonies on Czapek's solution agar growing restrictedly, attaining a 

 diameter of 1.0 to 1.5 cm. in 12 to 14 days (fig. 164A), margins abrupt, 

 colonies consisting of a fairly tough, closely woven, strongly wrinlded felt 

 in white to flesh shades, in some strains bearing limited conidial structures 

 to produce a light gray effect, in others producing abundant conidial struc- 

 tures in yellowish green to dark green shades approximating Russian green 

 (Ridgway, PI. XLII); exudate lacking or limited in amount; odor indis- 

 tinct; reverse at first colorless or nearly so in most strains, becoming vina- 

 ceous or orange-red either in localized areas or throughout; conidiophores 

 arising from the basal felt, sometimes branched, mostly less than 50/x in 

 length but ranging up to 100m by 2.5 to 3.0/x in diameter, walls smooth; 

 penicilli typically biverticillate and symmetrical (fig. 164D), but some- 

 times fractional or irregular; metulae usually in verticils of 5 to 7, mostly 9 

 to 12/i by 2.0 to 2.5m; sterigmata commonly in verticils of 5 to 8, acuminate, 

 about 10 to 12/x by 1.8 to 2.2^, but in individual strains often longer or 

 shorter; conidia eUiptical, 3.0 to 3.5m by 2.5 to 3.0m, with walls conspicu- 

 ously roughened, in tangled chains up to 50m or more in length. 



Colonies on steep agar growing more rapidly, 2.5 to 3.0 cm. in diameter 

 in two weeks, with limited central area raised, slightly floccose, dull gray 

 in color and with marginal zone 1 cm. wide radially furrowed (fig. 164B), 

 heavily sporing, in gray-green shades near artemisia to lily green (R., PL 

 XL VII); colony reverse ranging from colorless or drab to more or less 

 mottled in red and brown shades; penicilli as described above. 



Colonies on malt extract agar growing at about the same rate as on steep 

 agar but heavily sporing throughout (fig. 164C), plane, in dull yellow-green 

 shades, appearing almost velvety but with surface regularly showing a 

 thin loose network of white to yellow, sometimes encrusted aerial hyphae; 



