THE SPECIES OF THE GENUS PENICILLlUM. 337 



In re-naming the species, P. Rogeri would perhaps be more appli- 

 cable than P. Epsteini, suggested by LINDA u (II.). Thorn states 

 that the vegetation is white at first and decidedly woolly (not 

 smooth !), the colour gradually changing to pale greyish green, 

 and afterwards greyish white. The conidiophores are 300-800 p, 

 long and 3-4 jj. thick, the conidia heads are up to 175 p in length 

 and slightly branched. Sterigmata are not numerous (8-n p. by 

 2.4-3 /*) * ne r ip e conidia are globular (cylindrical to ellipsoidal 

 while young), bluish green, large, 4.5-5.5 \L thick and smooth. 

 The mycelial threads are about 5 jj. in diameter. Conidia are 

 formed on the free surface only, not in cavities in the substratum. 

 Sugar gelatin is liquefied under the colonies only, litmus being 

 turned red at first, but quickly blue again. Cheese inoculated 

 with this species is covered over in a week with a woolly white 

 mycelium. The fungus does not seem to occur in the open ; and 

 Thorn regards it as a typical dairy species which will not grow 

 under other conditions. Even as an infection, it rarely occurs on 

 other kinds of cheese. The conidia lose their power of germina- 

 tion if kept perfectly dry for a few weeks. It is said to peptonise 

 milk without any previous coagulation, and to assume a faint 

 yellow colour, without emitting the pungent ammoniacal smell 

 produced by " P. glaucum" (Roquefort-P.). The slight acidity 

 set up in the substratum at first, soon disappears. In pure 

 cultures, the species can be distinguished from the two preceding 

 ones at a glance. 



Penicillium luteum, Zukal, forms green vegetations, distin- 

 guishable from the other species by their faintly brownish (olive) 

 tone. The sterile mycelia are often characterised by a bright 

 lemon yellow coloration, which is afterwards masked by the 

 incipient conidia, and is then only visible at the edges, if at all. 

 It differs from the ordinary species by its small ellipsoidal conidia 

 and very long sterigmata. It frequently occurs on substrata 

 that are prone to mould (skins, fruits, paste, &c.), especially 

 preferring those of an acid character (lemons), and according to 

 BEIIRENS (IX.), it causes fruit to rot, by producing poisonous sub- 

 stances. On account of its tenacity and rapid growth, it is a 

 source of trouble in places where it has once found a lodgment, 

 and when infecting other fungi it frequently kills them oft' 

 rapidly. According to WEHMER (XXXIV.), this is especially 

 the case with Citromyces, on the vegetations of which it produces 

 brown, slippery, dead patches which rapidly spread outwards. 

 The tenacity of life on the part of the conidia is, however, very 

 slight ; and as a rule they all die off in one or t\vo years. The 

 delicate conidiophores (Fig. 179), more closely examined by 

 WEHMER (XX.), branch like the two preceding species, but are 

 characterised by a tendency to form whorls, so that the main 

 filaments usually exhibit only a single whorl of 2-4 branches of 

 the first order bearing tufts of sterigmata, though a variety of 



