ALCOHOLIC FERMENTS. 199 



partly by introducing, with every precaution, cultures of 

 Saccharomyces apiculatus into the soil and leaving them 

 during the winter. In the spring and early summer the 

 soil was again examined, and culture experiments proved 

 that the ferment was still alive in all the samples. Thus, 

 it was proved that the ferment can winter in the soil, and 

 it was also previously shown that it practically only occurs 

 at the stated places in the soil. In some more recent ex- 

 periments of Hans en's , vigorous growths of the ferment in 

 well-closed Chamber-land filter-tubes were placed below the 

 surface of the earth. After three years, the contents of the 

 tubes were introduced into sterilised wort, and a vigorous 

 development of the ferment was obtained. The period of its 

 life can thus extend beyond a year. 



Finally, it remained to be proved that the soil is its true 

 habitat during the winter ; in order to prove this, Hansen 

 examined the dust from the most diverse places from January 

 to June, also the dried fallen fruits of many plants, and finally 

 also various excrements. The seventy-one analyses gave a 

 negative result, and thus furnished the proof that the true 



O JT 



vsinter habitat of the ferment is the soil under the previously 

 mentioned plants. It retains its ordinary appearance during 

 the long winter-time, and in the summer it is again carried 

 into the air by the united action of insects and the wind, and, 

 through these two means of transport, it becomes further 

 distributed from fruit to fruit. 



It is evident that at the time when the ferment appears 

 in abundance on the ripe fruits mentioned, it may also be 

 carried by the wind to other places, and thus also on to 

 unripe fruits. Even in his first memoir, Hansen stated that 

 the reason of the rare occurrence on unripe fruits might be 

 that the ferment quickly perishes, partly from want of 

 nourishment and partly from the drying up of its cells. 

 Subsequently he proved by experiment the correctness of this 

 view. He stirred up with water partly old and partly young 

 cells, and placed them in thin layers, either on object-glasses 



