132 ^lORPHOLOGY AND LIFE-HISTORY OF YEASTS. 



brick. It was, however, shown by J. Chr. Nielsen (I.) and 

 Alb. Klcecker, that sporulation took longer on this substance 

 than on gypsum; on the other hand, equal results with the 

 latter are furnished by the clay cubes first employed by H. 

 Elion (III.). Th. Bowhill (I.) uses gypsum blocks of the same 

 shape (a cylinder, cut through slantwise) as the slices of potato 

 employed for streak cultures in test glasses; and he likewise 

 U3es these glasses. No advantage accrues from the substitution 

 of filter-paper for gypsum blocks recommended by E. Wasserzug 



(11.)- . , • 



The conditions with regard to access of moisture and air are 



also fulfilled by streak cultures on solid nutrient substrata; 

 and, as a matter of fact, ascospores are formed under such 

 circumstances— as was first observed by Hansen, and afterwards 

 by other workers. For example, the part of the gypsum block 



can also be played by a damp 



^^^^^^^m^^^ wall (in the brewery) towards 



^^SSsJJ---:^;:^^--=T^^ the ycast sprinkled thereon, or 



Sv,_ #'' ^^ac wfc'' 1^ by a damp filter-bag, &c., for 



W'l,, ™ :{;lS^4itL^^.... yeast gaining access thereto from 



'i^M^^'^^^^^W^^^ the air. Again, as is shown in 



if^^^ ^^^-- :^^^ &^^^-^^^- Fig. 141, spores may occasionally 



C^ ,^-^^.,l _l.._.:_ Jl ^^ - "^^ be observed in the development 



'" ', ,^„ of film; but these are merely 



Fig. 140.— Gypsum-block Culture. ' . rriv, • 



exceptional instances. 1 hen- 

 occurrence was vainly sought by H. Will in bottom-fermentation 

 beer yeasts. On the other hand these organs are, naturally, 

 not lacking in the films of the comparatively few Saceharomycetes 

 that grow almost exclusively in the form of film and not as 

 sedimental yeast, a special instance being afforded by Sacclu 

 membranaifaciens. Sporulation has also often been observed in 

 the interior of liquid cultures : by Hansen in repeatedly aerated 

 cultures of several species in yeast water, and in Saccli. Ludioigii 

 grown in 10 per cent, saccharose solution; also by H. Will. 

 (VIII.) in a wort culture of his bottom (beer) yeast No. 93 ; by 

 P. Roeser (II.) in a ij^er mil. solution of peptone ; and by Haute- 

 feuille and Perrey (I.) in a culture of wine yeast in must at 

 28° 0. When the nature of the question at issue necessitates 

 absolute purity of the spore culture, Hansen makes the sowing 

 on a thin layer of water at the bottom of a flask, and not on a 

 gypsum block in a glass basiu. 



With regard to the inception of sporulation we know com- 

 paratively less than we do of the conditions under which the 

 phenomenon occurs. In general it may be ssiid, according tO' 

 the determinations made by E. Chr. Hansen (XXVIII.), that 

 the cells do not resort to sporulation until they are unable to- 

 reproduce further by budding. Both old and young cells are 

 capable of producing spores, even such as have not put forth any 



