138 :»[ORPHOLOGY AND LIFE-HISTORY OF YEASTS. 



long as the membrane of the parent-cell continues to hold firm. 

 Consequently the ascus looks as though divided into compart- 

 ments. In some instances (see g) a coalescence of the spore 

 membranes occurs at the points of contact. In the case illus- 

 trated, the parent-cell contained three spores fused into one by 

 the coalescence of their membranes. On pressing the cover glass 

 this fused aggregation was expelled from the parent-cell, the 

 membranes of the three compound spores bursting simultaneously, 

 each in one place. A similar case is illustrated at e, but with 

 this difference that here the parent-cell contained four spores, 

 one of which remained behind after the application of^ pressure, 

 the parent-cell having contracted to its original dimensions. 

 Even without artificial aid the membrane of the parent-cell 

 finally gives way under the growing pressure and liberates the 

 spores, which then put forth buds (/') and henceforward behave 



^ U 



FIG. 145.— Saccharomyces cerevisife I. Hansen. 



a Three coherent spores issued from the parent-cell. «'. The same after riineteen 

 hours [n wort at 2o"c. in the Ranvier chamber. Two of the spores carry each a single 

 bud ft". After twenty-two hours ;«■". after thirty hours. „„^^/i iw Hie nnnpr 



b. A parent-cell with four spores; the two below are partly covered by the upper 

 pair b'. After eighteen hours (as with a'). The membrane ^^ ^h^, P^['l'?*:'^^;^„Ii^' 

 become torn, and hangs, like a veil, on the colony of cells formed fiom the spores. 

 Magn. 1000. (After HaiMen.) 



like vegetable cells. The extent of subsequent budding naturally 

 depends on the external conditions (nutrient media, admission 

 of air, temperature, &c.). Two examples are shown m Fig. 145- 

 In some instances the septum formed by the coalescing mem- 

 branes of two spores is absorbed and a fusion of the contents 

 of both spores occurs. The ascospore germination oi all the 

 yeasts employed in brewing, distilling and wme making follows 

 this first typical course. . 



An example of the second method of spore germination is 

 afforded by Sarrh. Lwlwiqii. Various genera of deciduous trees, 

 the oak in particular, frequently exhibit a mucinous flux which 

 is readily perceptible with a little care. In the earliest silage 

 of the complaint there exudes from the bark— both from frost 

 cracks, knot-holes, and apparently uninjured places— a white 

 froth, the smell of which is enough to show that a coliolic 

 ferments have contributed to its formation. For more detailed 

 investigations on the phenomenon we are indebted to J^R. 

 LuDWiG (II.). This exudation, which may also prove ot interest 

 to foodstuff chemists in connection with birch wme, was recog- 

 nised by him as the field of activity of various species ot mici;o- 

 organisms, the occurrence and action of which he traced m 



