88 MICRO-ORGANISMS AND FERMENTATION. 



or similar branches may also spring from the next cells, 

 and these again ramify and become pointed as described 

 above. In this tuft of branches each pointed cell (sterigma) 

 breaks up into a series of spherical conidia, and finally the 

 tuft carries a large number of conidia, arranged in series, 

 which, when ripe, are readily scattered. These round, smooth 

 conidia give to the patches of mould their greyish-blue 

 colour ; when they fall upon moist surfaces, they are able 

 to germinate at once. 



In culture experiments with this fungus, Brefeld made the 

 interesting observation that PeniciUium can occur under 

 certain conditions with an entirely different form of growth. 

 He enclosed cultures of this mould-fungus on slices of coarse, 

 non-acidified bread, between glass-plates, and allowed the 

 culture to further develop with the greatest possible exclusion 

 of atmospheric air. There then appear in pairs on the 

 mycelium short, thick branchings, which become entwined 

 (5, above) ; one part of this spiral throws out short, thick 

 filaments ((7), whilst the hyphal thread carrying the spiral 

 develops numerous fine branchings, which envelop the spiral 

 and form a covering (D), consisting of an inner solid and an 

 outer felt-like layer ; the inner cells gradually become coloured 

 yellow, and the outer loose cells are cast off. In this small 

 yellow ball sclerotium a formation of swollen cells (E, F,G} 

 gradually takes place by the continued branching of the 

 above-mentioned spiral filaments, and in each of these new 

 cells eight large and lenticular spores are produced, which 

 have a circular furrow on the margin, and three or four slight 

 ridges on the outer membrane (Exosporium). After the 

 collapse and absorption of all the remaining interior elements 

 the spores are at last set free, and the small yellow ball is 

 then filled with the spore-dust. The entire development 

 requires six to eight weeks. The sclerotia may be preserved 

 in a dry state for several years without losing their power of 

 germination. When the spores (H) are sown, the exosporium 

 bursts open like a shell at the circular furrow, and the endo- 



