178 BASIDIOMYCETES. 



of air, at a suitable temperature, an endogenous formation of 

 spores takes place. The protoplasm of the cells divides into 1-4 

 (rarely a greater number) masses (Fig. 182 c, d, e) which surround 

 themselves with a thick cell- wall, and in this state can with- 

 stand adverse conditions and periods of dryness lasting for several 

 months. 



The sporangia are not asci since they have no definite form, and 

 a definite number, form and size of spores is not found. The 

 spores in the different species and kinds occupy varying periods 

 for their development, although exposed to the same temperature, 

 a fact of importance in determining one from another. On 

 germination the wall of the mother-cell is destroyed, and each 

 spore gives rise to a new cell, multiplication taking place by 



budding (Fig. 182 /). The majority 

 of Yeast-Fungi are able to produce 

 alcoholic fermentation in saccharine 

 fluids. 



The most important of these 

 Fungi is the Beer-yeast (Saccharo- 

 mijcescerevisice) with ovate, ellipsoidal 

 or spherical cells (Fig. 182). It is 

 a plant which has been cultivated 

 from time immemorial, on account 

 of its property of producing alco- 

 holic fermentation in sugar-contain- 

 ing extracts (wort), derived from 



germinating barley (raalt ). C ar- 



bonic acid is also set free during this process. The " surface- 

 yeast " (Fig. 182 a), which produces ordinary beer when the 

 brewing takes place at higher temperatures, has cell-chains ; 

 " sedimentary yeast " (Fig. 182 b), used in the brewing of Bavarian 

 beer, has spherical cells, solitary, or united in pairs. Both these 

 and the following Yeast-Fungi include, according to Hansen, 

 several species and kinds. 



The " Ferment of Wine " (Saccharomyces ellipsoideus) produces 

 wine in the juice of grapes. Uncultivated yeast-cells are always 

 present on grapes ; an addition of this species to the " must " is 

 hot necessary to secure fermentation. A large number of other 

 " uncultivated " yeast-cells appear in breweries mixed with 

 the cultivated ones, and cause different tastes to the beer (S. 

 pastorianus, etc.). S. ludwigii, found, for instance, on the slimy 



