CHAPTER V. — COMPARATIVE REVIEW. — DOUBTFUL ASCOMFCETES. 27 L 



opinion. They have shown that the earlier observers obtained uncertain results 

 from having different and imperfectly distinguished forms mixed up together in 

 their impure cultures, and have revealed another source of obscurity in their belief 

 that every form of sprouting Fungus must be regarded as an inciter of fermentation 

 or 'Yeast-fungus,' and conversely that all alcoholic fermentation was caused by the 

 vegetation of a sprouting Fungus resembling Saccharomyces. We know now that 

 this is not so. 



But there are first of all many species of Fungi in which the only mode of vegetation 

 is by sprouting or which vegetate in this way under certain circumstances or in certain 

 stages of their development. Foremost among these are the ascogenous species of 

 Saccharomyces. Connected with the latter are the forms which resemble them 

 exactly in their vegetative construction, but in which asci and distinct spores are not 

 known, or it should be said perhaps are not yet known. These are usually, and for 

 the present rightly placed in the genus Saccharomyces ; whether they really belong 

 to it has yet to be ascertained ; among them are S. apiculatus which has been 

 so thoroughly examined by E. Hansen, and ' Pasteur's Torulae ' recently investi- 

 gated by the same observer. To these must be added Exoascus, also the plants 

 mentioned above on page 114 as examples 

 of germination by sprouting, and certain 

 Mucorini (see page 155) with further in- 

 stances in the Ustilagineae (see page 179), 

 Tremellineae, and Exobasidium recently 

 supplied by Brefeld (see section XCII). 

 Lastly, we must mention Fumago (see 

 page 249) on Zopf's authority, and a form 

 most probably nearly related to Fumago 

 or Pleospora and at present imperfectly 

 known, which I formerly described as 

 Dematium pullulans. It is very com- 

 mon on the surface of plants ; and for 

 this reason and because its sprout-cells 

 are very like those of some species of 

 Saccharomyces the two forms have no 

 doubt often been mistaken for one another 

 by earlier observers, who did not distin- 

 guish different forms very acutely. It is 

 probable that a similar confusion is at the 

 bottom of Pasteur's statement, that certain 



brown-walled cells which are found on succulent fruits are the resting-states of 

 species of Saccharomyces which excite fermentation. It will be well therefore to 

 repeat here my former description of the plant which has been confirmed by Low 

 (see Fig. 123). 



Small ellipsoid cells sprout in large quantities in a saccharine solution or in water 

 from the colourless branched and septate mycelial hyphae of Dematium, some from 

 the extremities of short branches, some from their sides. They are abscised and 

 multiply in exactly the same way as the cells of Saccharomyces. Finally, when the 

 available food is exhausted, the mycelial hyphae divide by transverse walls into cells 

 which are as long as broad and then swell into a roundish shape ; their membranes 

 also become thick and two-layered and of a brown colour, and they secrete small drops 

 of oil in their interior. The free sprout-cells show the same changes under similar 

 conditions. When they are again placed in a suitable fluid, each brown cell goes 

 through a period of rest, and then puts out a germ-tube, which proceeds to abscise 

 fresh cells either at once or after it has developed into a branched hypha. The 

 sprout-cells of Dematium attain a considerable size and then become of an elongate 



Fig. 123. Dematium pullulans. A, x x portion of a row 

 of cells with brown membranes forming tubes and occasionally 

 sprouts in a saccharine solution. B portion of a filament 

 vegetating in a saccharine solution and covered with sprout- 

 cells. A magn. 390, B nearly 200 times. 



