264 



GENERAL BOTANY 



PENICILLIUM (BLUE MOLD) 



Habit. The common blue-green molds are found on decaying 

 fruits, vegetables, and foods of various kinds. They differ from 

 the black molds in that their hyphse are subdivided into many 

 cells, each cell of which is provided with a single nucleus. 

 They also produce asexual spores by the transverse division of 

 special spore-bearing hyphse and not by cell division within a 



sporangium, as in Rhizopus. 

 When fruits or other 

 nutrient media suitable for 

 the growth of Penicillium 

 are left in a moist place, 

 white patches of mold are 

 almost certain to appear in 

 two or three days on the 

 surface of the exposed sub- 

 stance (Fig. 143). Careful 

 examination of these areas 

 will reveal more or less 

 radiate patches of hyphse 

 constituting the young 

 mold colonies of Penicil- 

 lium. This radiate appear- 

 ance will be found to be 

 due to the fact that the 

 new hyphse which make up the white mycelium of the mold 

 are growing out centrifugally from the point where the mold 

 spores started to germinate. This centrifugal growth continues 

 until neighboring patches unite into one extensive mycelium, 

 thus obscuring the method of origin. 



The patches of mycelium described above start from spores 

 which have been deposited from the air on any given nutrient 

 medium. These spores germinate, like those of Mucor already 

 described, by the rupture of the outer coat of the spore and the 

 protrusion of the inner coat to form a hyphal filament. If 

 spores of Penicillium are sown on prune juice or on some other 



FIG. 143. Decay of apples caused by 

 mold growth 



The mycelium of the mold penetrates the apple, 



as in the case of Rhizopus on bread (Fig. 140), 



and breaks down its substance, thus causing 



decay. After Conn 



