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. Van Tieghem* showed that the mycelium of Penicillium and of 
Aspergillus niger when growing in sclution 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 other 
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 ost 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 Gährung, as cited on page 188. —Gayon in Comptes rendus, 86 (1878), p. 52, 
and in Ann. Chim. et. Phys. XIV (1878), p. 258. 
? Ann. d. sc, nat. ser. 5, VIII (1867), p. 210. 
