358 DIVISION III. -MODE OF LIFE OF THE FUNGI. 



Saccharomyces which excite fermentation, but the forms or species of which he does 

 not determine, are found in abundance at harvest time on grapes and on their stalks, 

 while they are rarely or never found at a later time on grapes which have remained 

 through the winter and on young grapes in summer ; this means that those cells which 

 may happen to have survived have at least become incapable of development. 



Few saprophytic Fungi are known to be specific ferment-organisms, if we judge 

 of them by their effect on the substratum. Several species of Saccharomyces are the 

 Yeast-fungi of alcoholic fermentation, and near them come species of Mucor which 

 produce a similar kind of fermentation. The power of producing fermentation is a 

 specific peculiarity, as has already been pointed out on page 271, and not confined to 

 any particular growth-form, as that of the Sprouting Fungi for example. It is wanting 

 among the Saccharomycetes in the flowers of wine, Saccharomyces Mycoderma or 

 mesentericus, and perhaps in some others ; it varies in the forms which excite fermen- 

 tation according to the species, all other conditions being the same. Of the Mucorini, 

 Mucor racemosus, M. circinelloides, and M. spinosus cause a tolerably active fermen- 

 tation in the sugar, while the activity of M. Mucedo is small, and that of M. stolonifer 

 is scarcely greater l . Van Tieghem a showed that the mycelium of Penicillium and of 

 Aspergillus niger when growing in solution of tannin breaks up the tannin into 

 gallic acid and glycose. 



The ferment-secretions have already been noticed on page 355. It is almost 

 certain that further investigations will show the existence of fermenting power in oiher 

 saprophytic Fungi. 



It is known that the final result of the process of vegetation in most of the 

 saprophytes which have been examined is a combustion of the organic substratum. 

 Penicillium also and Aspergillus niger cause combustion of the tannin when they 

 vegetate on the surface of the solution with an unlimited supply of oxygen. 



4. PARASITES. 



SECTION CI. We have little exact knowledge of the chemico-physiological pro- 

 cesses in the life of the parasitic Fungi, because the symbiotic relation puts great 

 complications and difficulties in the way of their precise investigation. 



We encounter on the other hand in these Fungi a very long and varied series of 

 phenomena of one-sided or reciprocal adaptation between the parasite and the 

 living organism on which it feeds, and some of these phenomena are of a very 

 obvious character. In contemplating them we have to set out from the following 

 general considerations. 



The plant or animal on which a parasite lives is termed its host or feeder. 

 Every parasite species lives on certain host-species, and the limits within which it can 

 choose its host are different in different species. Some parasites have never been ob- 

 served on more than a single host, Peronospora Radii for example on Pyrethrum ino- 

 dorum, Uromyces tuberculatus on Euphorbia exigua; so Cystopus Portulacae, Rhytisma 

 Andromedae, Triphragmium Ulmariae and T. echinatum, and many other species that 



1 Brefeld, Ueber Calming, as cited on page 188. Gayon in Comptes rendus, 86 (1878), p. 52, 

 and in Ann. Chinu et. Phys. XIV (1878), p. 258. 

 3 Ann. d. sc. nat. ser. 5, VIII (.1867), p. 210. 



