134 ORIGIN OF THE YEASTS 



tures could explain the results of these two workers. In repeating the 

 investigation on Gl. nervisequum he showed that this fungus never 

 produced the yeast-like structures when grown in certain media. 

 On the other hand, he established that the yeasts which these workers 

 thought they observed as derivatives of GL nervisequum present the 

 same characteristics as the yeast-like structures of a species of De- 

 matium which he observed in the earlier inoculations of the Gloeo- 

 sporium. This Dematium exists on all of the leaves of the plane tree 

 and develop, almost always, in a state of impurity in the first arti- 

 ficial cultures of GL nervisequum. Then, to such data, Guilliermbnd 

 attributes the conclusions of Viala and Pacottet. As for the endo- 

 spores described by Viala and Pacottet in the yeast structures, they 

 may have been simply fat droplets from old cells of Dematium which 

 by the size and regular positions resemble the endospores of yeasts. 

 Whatever is the case, it is definitely established that GL nervisequum 

 does not form yeasts 



(B) Studies in Life Cycles of Yeasts in Nature 



This conclusion on the transformation of yeasts is fully confirmed 

 by the careful investigations of Hansen l on the life cycles of yeasts. 

 The first observations of this author date back to 1881, and are con- 

 cerned with Saccharomyces apiculatus. This yeast is particularly 

 adapted to life history studies on account of the special form of its 

 cells. (Fig. 6.) Hansen observed that this yeast existed on many dif- 

 ferent fruits and that it was found only on the walls. It was only 

 present on the fruits and not on other parts of the plant. It appears, 

 then, that it lived only where there was sugar or where it was able to 

 multiply. 



Hansen thought that the rain and decay of the plant carried this 

 to the ground on which fruit trees grow. It seems, then, that this 

 yeast is able to hibernate in soil near fruit trees. If samples of this 

 earth are taken in the springtime, S. apiculatus is always found. Finally 

 to prove this hypothesis, he inoculated soil and left it out through 

 the winter. From time to time, he sampled this soil and always 

 found Saccharomyces apiculatus. Hansen has thus demonstrated that 

 Saccharomyces apiculatus is able to perpetuate itself in the soil from 

 year to year. 



1 Hansen, E. Recherches sur la physiologic et la morphologie des ferments 

 alcooliques. Sur le S. apiculatus et sa circulation dans la nature. Comp. Rend, 

 du lab. de Carlsberg, 1, Livr. 4. 1881. Nouvelles recherches sur la circulation du 

 S apiculatus dans la nature. Ann. des. Sc. nat. et botanique, 7th Series, 1890. 



