CIDER YEASTS OF PEARSE AND BARKER 249 



at 25 C. The ascs formed by the ellipsoidal cells form only three or 

 four ascospores; those from the large cells form nine or ten. The 

 ascospores are round and very refractive. After long culturing in 

 must sugar solutions, this yeast loses its ability to sporulate. Sac- 

 charomyces multisporus is a bottom yeast which adheres closely to 

 the culture flask, so well that it is difficult to detach it. A thin scum 

 is formed. It yields about 4 per cent of alcohol by volume and pro- 

 duces a disagreeable taste. This yeast ferments dextrose, maltose, 

 and saccharose. 



SACCHAROMYCES MALI RISLERL Kayser 1 



Discovered in specimens of cider by Kayser, this yeast possesses 

 spherical cells, from 4 to 6 microns in diameter, which have a thermal 

 death point of 60 C. Oil liquid media, they produce an adhesive 

 deposit on the walls. The ascospores form at 15 C. at the end of 

 ninety hours. This species ferments saccharose, dextrose and maltose. 



CIDER YEASTS OF PEARSE AND BARKER 



These species have been isolated by Pearse and Barker 2 from 

 ciders in Alford and Kingston, England. 



Yeast A. The cells in beer wort are usually oval while in old 

 cultures they become elongated. The cells developing on gelatin 

 sometimes take the form of sausages. The maximum temperature 

 for budding is situated between 35 and 38 C. Spores are easily formed 

 in 90 hours on potato and porous porcelain at room temperature. 

 They commence toward 15 and stop at 26 C. They are often ob- 

 served also in old cultures on wort. The ascospores measure 3.1 

 microns in diameter. At the time of germination the wall of the asc 

 is ruptured, the ascospores swell and germinate by normal budding. 

 On gelatin this yeast forms dry spherical colonies, with slightly in- 

 dented border. On streaks, it produces a creamy vegetation, with 

 folded, slightly fringed borders. It liquefies gelatin very slowly. This 

 species ferments saccharose, dextrose, levulose and maltose. 



Yeast B. This yeast is much like the preceding one in which the 

 cells have the same shape. Their dimensions vary between 6.8 and 

 10.2 to 4.4 ju. The maximum temperature for budding is around 33 C. 

 Sporulation is accomplished easily on carrot and on porous porcelain. 

 It appears on this last substrate in about 42 hours at 26 and in 90 



1 Kayser, E. Etude sur la fermentation du cidre. Ann. Inst. Pasteur, 4, 1890. 



2 Pearse, B., and Barker, P. The yeast flora of bottled ciders. Jour. Agricul- 

 tural Science, 3, 1908. 



