SECT. in. YEAST OF BEER. 287 



in all kinds of liquids, and in almost all kinds of condi- 

 tions ; even the peculiar knotty filaments observed in its 

 submerged mycelium are not constant in different 

 liquids. M. Hoffmann has observed with certainty 

 the passage of Penicillium glaucum into Penicillium 

 candidum, into a sulphur-coloured Penicillium, and, 

 lastly, into the Coremium glaucum, so that this fungus 

 is polymorphous, although the conditions under which 

 the changes take place are unknown. 2 



It appears that substances and liquids do not ferment 

 spontaneously, for upon examining with a microscope the 

 dust obtained by scraping the exterior of gooseberries, 

 plums, vine leaves, potatoes, &c., M. Hoffmann found the 



Fig. 35. Torula Cerevisiae, showing successive stages of cell-nraltiplication. 



short chains of the Torula, the necklace-like ferments 

 of the Hucedines, and the chaplets of others. Some had 

 already begun to germinate, and were developed readily 

 when put into water. They had no doubt been carried 

 by the wind from the dry refuse of fermented substances 

 which are thrown away. 



The yeast of beer was at one time considered to con- 

 sist entirely of the cells and chains of the Torula Cere- 

 visise (fig. 35). This, which is one of the Coniomycetes 

 of the order Torulacei, is in its early stage a colourless 

 transparent globe capable of endless increase by budding. 

 When in a liquid favourable to its growth, as the wort 

 of malt, buds in the form of young cells spring from the 

 walls of the globes ; these soon become perfect and 

 acquire buds also, so that in a few hours the parent cells 



2 Memoir by M. Hermann Hoffmann, upon Fermentation, in the ' Ann. 

 des Sciences Naturelles,' 4me serie, 1860. 



