206 A MANUAL OF THE PENICILLIA 



Members of this series appear to be fairly abundant in nature and are 

 world-wide in distribution. They regularly occur in soil dilution plates, 

 but due to their restricted growth may be easily overlooked, or become 

 quickly overrun by more vigorously growing species. They are appar- 

 ently better adapted to growth in the presence of limited nutrients, or 

 under alternate wet and dry conditions, than many Penicillia, for they 

 occur with unusual frequncy among the molds isolated from military 

 equipment undergoing deterioration under field conditions. 



The Penicillium decumhens series, as it is considered here, includes a 

 range of forms rather divergent in some respects but uniformly charac- 

 terized by the production of small monoverticillate penicilli borne on short 

 branches (or conidiophores) arising from trailing or interlacing hyphae 

 (fig. 56) Upon the basis of general colony texture, the series can be 

 subdivided into two fairly well defined sub-series. 



The first of these, typified by Penicillium decumhens Thom, is character- 

 ized by comparatively slow growing but loose-textured colonies in which 

 the trailing, penicilli-bearing hyphae are loosely interwoven and retain 

 considerable individuality (see fig. 57C). In addition to P. decumhens, 

 this sub-series includes P. chermesinum Biourge, which is characterized by 

 its more rapid growth and its development of bright red colors in colony 

 reverse on malt and wort agars. 



The second sub-series, typified by Penicillium Jellutanum Biourge, is 

 characterized by the development of restricted, tough, almost leathery 

 V)asal felts, from the surface and margins of which arise trailing aerial 

 hyphae bearing small penicilli on short conidiophores in the manner typical 

 of the series. Also, included here are P. citreo-viride Biourge, a very 

 slow-growing, tardily sporulating form which produces small, raised colo- 

 nies with surface and reverse bright yellow on Czapek's solution agar; and 

 P. roseo-purpureum Dierckx, equally slow-growing, tardily sporulating 

 and almost floccose, producing abundant orange-red to vinaceous pigment 

 in the exudate and the colony reverse. 



Penicillium chermesinum Biourge, in Monograph, La Cellule 33: fasc. 1, 



pp. 284-285; Col. PI. X and PI. XVI, fig. 95. 1923. Also Thom, 



The Penicillia, pp. 192-193. 1930. 



Colonies on Czapek's solution agar growing fairly rapidly, attaining a 

 diameter of 4.0 to 5.0 cm. in 2 weeks at room temperature, broadly zonate, 

 radiately wrinkled and buckled, surface tufted, granular (fig. 57A), con- 

 sisting of a woven mass of hyphae and ropes of hyphae bearing conidio- 

 phores as short branches, rather light sporing, fruiting areas in greenish 

 gray shades near mineral gray (Ridgway, PI. XLVII), unevenly distrib- 

 uted, generally denser in central areas, conspicuous zones sometimes evi 



