CHAPTER V. COMPARATIVE REVIEW. DOUBTFUL ASCOMYCETES. 



Four hemispherical spores are formed in each ascus, which escape when mature by 

 the dissolution of the wall of the ascus, and put out germ-tubes in water. Nothing 

 more is known of this species ; the controversy which has arisen in the attempt to 

 determine it will be noticed again in section XCIII. 



SECTION LXXVII. The chief representatives of the genus Saccharomyces 

 are the Yeast-fungi which excite alcoholic fermentation and are known as Sac- 

 charomyces Cerevisiae, S. ellipsoideus, S. Pastorianus, &c. These names, according 

 to E. Hansen's recent investigations, denote form-groups, which will no doubt have 

 to be otherwise distributed. Besides these there are the Flowers of wine, S. Myco- 

 derma, Reess, Cienkowski's Chalara Mycoderma, and the Fungus of thrush (apthae), 

 S. albicans, Reess, which grows as a parasite on the mucous membrane of the 

 human digestive organs, but also thrives in saccharine fluids, where it excites a slight 

 fermentation. The rest are found in quantity in or on fluids which are fermenting 

 or have undergone fermentation. S. Cerevisiae is added intentionally to the wort of 

 beer and is cultivated largely for this purpose. Other kinds and indeed S. Cerevisiae 

 as well appear of themselves in must, finding their way into it chiefly from the 

 surface of the juicy fruits which yield the must. 

 They are conveyed to these fruits along with 

 dust from the surfaces of other bodies (see be- 

 low, section C). 



The larger part of these Fungi vegetate, 



as far as we know, only by sprouting (Fig. 121). <| 



Continuous branching hyphae with long seg- 

 ments are found only in Saccharomyces 

 albicans, in S. Mycoderma and Cienkowski's 

 Chalara ; these grow directly, according to 

 Cienkowski's observations on S. Mycoderma, FlG - ' Saccharomyces <;. ceiis before 



rotin b d cells sprouting in a fermenting saccharine 



from CellS formed by SprOUting, produce freSh solution. Successive stages of development according to 

 J the letters. Magn. 390 times. 



cells from their sides by sprouting, and ulti- 



mately divide transversely into short cells which then vegetate simply by sprouting. Other 

 species, especially Reess' S. Pastorianus, show a certain approach to this growth-form in 

 that they are frequently chains of elongated sprout-cells, from which short cells are 

 abscised laterally. The shape moreover of the single sprout varies generally between 

 spherical and elongated cylindrical, with certain rules and limitations in each species. 

 The cells that are formed one after another by sprouting in the fermenting fluid are 

 usually at once separated from one another ; connected strings of cells are to be seen 

 when the plant vegetates on still surfaces, such as a microscopic slide especially, and 

 the length and number of the chains vary according to the species. The cells of 

 S. Cerevisiae, when developed in large quantities, often adhere together irregularly 

 and form largish lumps, being attached to one another apparently by the muci- 

 laginous outer lamellae of their membranes (see on page 9). The structure 

 of the sprout-cells is that of other vegetative fungal cells, but their membranes are 

 comparatively thin and colourless. 



The Saccharomycetes in the sprouting form may be said to be capable of 

 unlimited growth and multiplication if supplied with sufficient food. This is shown 

 by the hundreds of thousands of pounds weight of yeast which are produced year by 



