FUNDAMENTAL RESEARCHES. 251 



are capable of producing endospores on the surface of the ground. 

 On the basis of these experiments Hansen was able, in his second 

 communication in 1882, to demonstrate that the life history of the 

 true Saccharomycetes is substantially identical with that of Sacch. 

 apiculatus. The chief breeding-place is on sweet, juicy fruit, the 

 soil constituting the winter habitat, whilst the principal methods 

 of transport are the wind, rain, insects and other small animals. 



The inoculation experiments were repeated subsequently by 

 HANSEN (LIX. and XLIII.) both with Sacch. apiculatus and with, 

 in part, the same Saccharomycetes (viz., Sacch. ellipsoideui, Sacch. 

 PastorianuSj Oarlsburg bottom yeast No. i and a top-fermentation 

 beer yeast), but in this case the flower-pots were replaced by 

 Chamber-land earthenware pipes, in order to ascertain whether the 

 yeasts could survive for several years in the soil. The earthen- 

 ware pipes were used in order to protect the cells, as far as 

 possible, from infection and the ravages of animals from the 

 surrounding earth. In the result it was found that the yeasts in 

 question are able to live for more than three years in soil. 



Both at that time and subsequently, the question of pleomor- 

 phism in these fungi was actively discussed, especially in con- 

 sequence of the researches of Brefeld, and Pasteur's theory of the 

 development of Saccharomycetes from brown Dematium cells must 

 be classed in the same catagory. It was considered possible that 

 still living original forms of these yeast fungi might be discovered, 

 and probably of such a character as to point to a very different 

 life history to that established by the researches on Sacch. apicu- 

 latus. Hansen himself, by referring to this possibility in several 

 of his later publications, not only led to the following up of this 

 line of research by several workers, but also to the institution of 

 experiments by others with a view to upsetting the theory he had 

 commenced to establish in connection with the life history of 

 yeasts. 



The repetition of Hansen's experiments, especially in connection 

 with the analysis of vineyard soils, became a matter of practical 

 and theoretical importance ; and in 1889 a series of investigations 

 in this direction was undertaken by H. MtiLLER-TnuRGAu (XXIX.). 

 This worker, also, found that the chief breeding-place of the 

 Saccharomycetes is on fruit, and that the cells of wine yeasts can 

 be discovered in soil all the year round. His experiments were 

 made in a vineyard at Geisenheim, and he was the first to 

 ascertain how deep yeast cells can be embedded in the earth and 

 continue to live, namely, 8-12 inches on the average, none being 

 found as deep as 1 6 inches. In the summer time the number of 

 yeasts cells on the surface is smaller than at a depth of a few 

 centimetres. At the outset, Miiller-Thurgau N held the opinion 

 that insects formed the chief means of transporting the yeast cells, 

 and he declined to admit the importance of wind in this connec- 

 tion. Hence the only point on which he was in complete accord 



