STUDIES OF LIFE CYCLES IN NATURE 135 



On the other hand, he has shown that it passes the winter in the 

 soil, for he examined other substances such as 'dust, dried fruit, ani- 

 mal excrement and never found this yeast. 



The investigations of Muller-Thurgau l and Berlese 2 indicate 

 somewhat the same things. Berlese has found, in April and June, 

 Saccharomyces apiculatus, ellipsoideus and Pastorianus in the earth 

 of vineyards and orchards. These yeasts were found down to 12 or 

 13 centimeters in depth and seemed to be equally distributed in both 

 sunny and shady places. This is interesting for it shows the resist- 

 ance of these yeasts to sun and light. Berlese has also found S. 

 apiculatus on the bark of oak and olive trees, and also in the nectar 

 of flowers. 



Hansen 3 has undertaken, in recent years, a study of the life cycle 

 of yeasts in nature to find out whether all of the yeasts behave like 

 S. apiculatus. He used various yeasts in this investigation and 

 experienced some difficulty, for the shapes of the various yeasts did 

 not lend themselves to a ready recognition. They were very easy 

 to confuse with the yeast forms of Dematium and other fungi. Only 

 one character was available and that was the formation of endospores. 



In his recent investigations, Hansen investigated the presence 

 of yeasts in the soil about Copenhagen and whether they were present 

 at all periods of the year. These environs included many orchards, 

 gardens and vineyards. He was scarcely able to find a spot which 

 did not contain yeast. They were almost always present in the sur- 

 face layers and scarcely at all in the deeper layers; at all times of 

 the year he was able to isolate them. The soil in vineyards and or- 

 chards was plentifully supplied with them but they diminished in 

 numbers as one went away from the orchards. Thus, in 100 analyses 

 of soil under fruit trees, 67 showed the presence of yeasts; away from 

 such places in fields, only 19 per cent of the samples indicated the 

 presence of yeasts. 



Hansen has also observed yeasts in the soils of beech, fir, pine 

 and oak groves but much less numerous than in fruit groves. Only 

 30 per cent of the samples yielded the presence of yeasts. Such 

 yeasts belonged to special genera such as Pichia membranefaciens 

 and Willia anomala. 



1 Muller-Thurgau, H. Ueber den Ursprung der Weinhefe. Weinbau Weinh. 

 No. 40 and 41, 1889. 



2 Berlese, A. Verhalten des Saccharomyceten an den Weinstocken iiber die 

 Verteilung der alkoholischen Fermenten in der Nature. Ueber die Transport- 

 mittel der alkoholischen Fermente. Rivista di patol. vegetale 5, 1897. 



3 Hansen, E. C. Neue Untersuchungen iiber den Kreislauf der Hefenarten 

 in der Natur. Cent. Bakt. 10, 1903. Ueber die Brutstatten der Alkolholgarungs- 

 pilze oberhalf der Erde. Cent. Bakt. 14, 1905. 



