136 ORIGIN OF THE YEASTS 



These investigations indicate that all of the yeasts studied by 

 Hansen have a life history identical with that of S. apiculatus. The 

 yeasts hibernate in the soil. They seem to differ only in their distri- 

 bution. Hansen explained this on the basis of spore formation, as- 

 suming that yeast which formed no spores would be killed. On the 

 other hand, thanks to the presence of spores, the yeasts live a longer 

 time than S. apiculatus in the ground water which carries them for 

 longer or shorter distances. 



It is then necessary to determine the method by which the yeasts 

 are transferred from the soil to the fruit skins. Transportation 

 through the air seems to play an important role. Chamberland has 

 observed that there are many yeasts in the air especially during sum- 

 mer and autumn. One may detect them at the other seasons but 

 they are not so common. From this the yeasts seem to be less 

 abundant during the rainy seasons of the year. Hansen l states that 

 yeasts are always found in the atmosphere but in different numbers. 

 Their number seems to be increased during June to August and es- 

 pecially at the beginning of September. During the other seasons, 

 one may not find them as readily. Berlese did not find any 

 yeasts in the air during April and May but was able to find S. 

 apiculatus in the beginning of June and during July. Thus it seems 

 that the air may be an important factor in transporting the yeasts 

 from the ground to the fruit. On this, they find a higher tempera- 

 ture and more favorable environment and develop to maturity. The 

 presence of yeasts, then, in the air seems to be a function of two fac- 

 tors: first, an active development of these organisms on the skin of 

 the fruit and, secondly, an absence of rain. 



Boutroux 2 has shown that insects play an important role in the 

 distribution of yeasts. He disclosed the presence of yeasts on various 

 insects (mosquitoes, wasps, bees, gnats and ants). Saccharomyces 

 cerevisiae, ellipsoideus and Pastorianus were demonstrated. Wort- 

 mann and Berlese have observed the same things and regard the insects 

 as the important mode of distribution of yeasts from grape to grape 

 and from vine to vine. In this way, Berlese explains the presence of 

 S. apiculatus in the nectar of flowers which has been visited by 

 Vespa crabro in which he has observed the same yeast. He does not 

 regard the deposition of the yeasts by the insects' feet with much favor 

 but points out that the yeasts are able to pass through the intesti- 



1 Hansen, E. C. Recherches sur les organismes qui a differentes epoques de 

 1'annee, se trouvent dans 1'air a Carlsberg et aux alentoirs. Comp. Rend, du 

 lab. de Carlsberg, 1, 1882. 



2 Boutroux, L. Sur 1' habitat et la conservation des levures apontanees. Bull, 

 de la Soc. Linn, de Normandie, 3rd Series, 7, 1883; Ann. des Sc. nat. Bot. 17, 1884. 



