ALCOHOLIC FERMENTS. 163 



containing mineral salts, sugar, and asparagine, with an addition 

 of citric or tartaric acid, such durative cells occur also in the 

 bottom-growth. From these cells germinate globular or oblong 

 yeast-cells, either singly or in large number (Fig. 45 A). 

 Especially in older cultures of the durative cells that have 

 formed in mineral nutrient solution there frequently spring up 

 club-shaped cells with transverse-wall formations, which 

 phenomenon may recur in derived growths (Fig. 455). During 

 germination on a solid nutrient medium, WILL also observed a 

 splitting-up of these transverse walls (Fig, 455). 



(d) The Temperature Limits for the Saccharomycetes. 

 Just as the influence of temperature on the development of 

 spores and films varies with the different species, so it has been 

 shown by HANSEN'S investigations (1883) that both spores and 

 vegetative cells of different species possess unequal powers of 

 resistance to hot water. In this respect the spores have a 

 greater resisting power than the vegetative cells. 



In experiments of this nature, as in the cases previously 

 discussed, the condition of the cells has a most marked effect 

 on the results ; they are especially influenced by age. Thus, it 

 was found that the cells of Sacch. ellipsoideus II., which had 

 been cultivated in wort for two days at a temperature of 27 C., 

 were killed in five minutes when heated to 56 C. in sterilised 

 distilled water, whilst cells of a similar culture 2J months old 

 were able, under identical conditions, to withstand five minutes' 

 heating to 60 C. without being killed. 



Eipe spores of the same species, which had been developed 

 at a temperature of 17 to 18 C., and, in the course of eight 

 days at the same temperature, had partially dried up, withstood 

 a temperature of 62 C. for five minutes, but were killed at 

 66 C. 



In the case of Sacch. cerevisice I. the vegetative cells are, 

 under similar conditions, killed by five minutes' heating at 

 54 C., whilst at 62 C. the spores are killed. 



An interesting grouping of HANSEN'S six species with 

 reference to a fixed temperature is also exhibited when they 

 are cultivated in wort under conditions favourable to film- 

 formation (see above). When, for instance, a temperature of 

 36 to 38 C. is employed for the development, the three 



