THE SPECIES OF THE GENUS PENICILLIUM. 343 



conidia, sometimes warty (5-7 p.). These statements, however, 

 require correction, the conidia being extremely variable in cultures 

 on different substrata, both elongated, pear-shaped, ellipsoidal, 

 spherical, smooth, prickly and warty forms being met with. The 

 typical development on a good substratum (wort gelatin), how- 

 ever, furnishes ripe conidia that are decidedly warty globules 

 with broad stems, the globules themselves soon falling asunder. 

 At an earlier stage they are elongated, sometimes pointed, and 

 also provided with a decided stem (see also Fig. 177). Mature 

 specimens measure 6.8-9.2 by 5.7-6.8 ^. Consequently these 

 conidia differ in a marked degree from those of all other species 

 of Penicillium. No sclerotia ascospores have yet been observed. 

 The species grows at only a moderate rate on the usual bacterio- 

 logical substrata, and liquefies gelatin. The optimum tempera- 

 ture of growth is about 2o-23 C., and development is sluggish 

 below 15 C. According to Stoll, a decided liberation of ammonia 

 is produced on alkaline gelatin, but not on sugar or acid gelatin. 

 Occasionally the spores are produced directly on the mycelium., 

 without sterigmata or supports (see drawing). This observation 

 needs reinvestigation, as indeed does the whole morphology of the 

 species, the existing communications on the subject being scanty. 



The following species are less known, apparently scarcer and 

 of no practical importance : 



Penicillium purpurogenum, Stoll, was described by STOLL (I.), 

 who obtained the species from Krdl, according to whom the 

 original culture was isolated by Fleroff from impure Japanese 

 koji. In respect of the conidiophores, colour of the vegetation, 

 and the formation of pigment, it resembles P. luteum. The vege- 

 tation is dark green to dark greyish green ; the conidiophores are 

 delicate and branched in whorls, each twig being usually provided 

 with four elongated, pointed sterigmata (7 by 2 jj,}. The conidia 

 are ellipsoidal, very small (2.8 by 1.7 yu), and uniform in size and 

 shape. The optimum temperature is about 30 C., growth ceasing 

 below 15 C., though the fungus continues to develop at incuba- 

 tion temperature. It produces a yellowish red to purple-red 

 pigment, but only on substrata containing carbohydrates. The 

 sterile mycelia are bright yellowish red. 



Peniciliium rubrum, Stoll, is a species of unknown origin, 

 isolated by Grassberger. and described by STOLL (I.) in 1904. 

 The hyphre are coloured yellow to yellowish red by excreted 

 granules; the conidial herbage dark green, and the conidiophores 

 are delicate and often branched in whorls, the ends of the twigs 

 carrying 4-5 long, pointed sterigmata (9.6 by 2 p). The conidia 

 are globular, very small (2.3 fj. in diameter), and- joined in readily 

 detachable short chains. The optimum temperature is 3o-35 C. 

 The species continues to grow at incubation temperature, but does 

 not develop below 15 C. It produces a yellowish red to rusty 

 brown pigment, but only on substrata containing carbohydrates, 



