Such, at least, is one interpretation of the facts that we have reviewed. The observations in the following paragraphs and chapters may the more incline our readers to accept it as the true one. § II.—Growth of Mycoderma Vini in a state of Purity—Confirmation of our original Conjectures as to the cause of Fermentation—Mycoderma Vini does not Change into Yeast, although it may give rise to Fermentation. The efflorescence of wine, cider, and beer is pretty generally known.[64] Fermented liquors cannot be exposed to the air without soon becoming covered with a white film, which grows thick and becomes wrinkled in a marked manner in proportion as it is deprived of room wherein to spread horizontally, in accord with the extraordinary multiplication of the cellules that compose it. The rapidity of this multiplication is sometimes astounding. During the heat of summer, when the medium is well adapted to the life of the plant, we may count the number of cells which grow in the course of a few hours by millions. The absorption of the oxygen necessary to the activity of this growth, and the heat developed in the film, as well as the liberation of carbonic acid gas, that result from it are considerable. A piece of glass covering the mycoderma, at some distance above it, becomes wet with moisture, that soon accumulates to form large drops of water. The quantity of oxygen absorbed is so great that we never see any other fungoid growth on the surface of this film, although the air is constantly depositing on it, as dust, spores of an entirely different character; for, notwithstanding that the warm and moist surface is in contact with an atmosphere that is being continually renewed, yet the _mycoderma_ appropriates to itself all the oxygen contained in the air. When, however, the vegetation begins to languish, we often find, on the other hand, that the plant becomes associated with other species of mycoderma, notably _mycoderma aceti_, as well as other fungi, amongst which _penicillium glaucum_ generally appears. This is one of the facts which, wrongly interpreted, have led to the belief that _mycoderma vini_ or _cerevisiæ_ may possibly, or even readily, become transformed into _penicillium_, and _vice versâ_.[65] As the study of the growth of _mycoderma vini_ on the surface of saccharine liquids and in their depths, unaccompanied by any other species, has the most important bearing on the theory of alcoholic fermentation, we may pursue it through a few examples with all the detail that it allows of. [Illustration: Fig. 22.] On June 21st, 1872, we sowed some _mycoderma vini_ in three flasks, with double necks, A, B, C (Fig. 22), containing some wort. The spores employed for the purpose were obtained from plants growing on sweetened yeast-water in an ordinary closed flask. This had been impregnated with spores from plants grown on wort, which in turn had sprung from spores taken directly from _mycoderma vini_ growing on wine.