yellow. The sporangia are colourless to yellowish, spherical, about 50 μ in diameter, smooth and translucent. The columella is spherical, smooth and colourless, and the spores are long shaped (5 x 2.8 μ), seldom round, colourless, smooth and shining. The best growing temperature for the fungus is 30° to 40° C. It is found on rice husks, and is made from these into "Chinese yeast," which is a common article of commerce in East Asia, and which contains, be

FIG. 61.-Mucor corymbifer, Cohn. Mycelium with underlying branched carriers. The sporangia at o have burst and the columella together with the expanded end of the carrier form a pear-shaped body. 27. (After Lichtheim.)

sides this species, various saccharomycetes, aspergillæ and bacteria. Its function consists, like that of the above species, in changing the rice starch into sugar, and thus making the latter capable of fermentation. This fungus can ferment sugar itself, like most other species of Mucor, but the process is best performed by saccharomycetes. The species has begun to be used, of late years, in spirit manufacture, but, as it seems, without real success.

Mucor spinosus, van Tieghem (Fig. 60), is distinguished by the thorny, irregular growths frequently found on the columella (Fig. 60, II.); these sometimes appear only as bacterium-shaped growths, or they may be entirely absent. If the fungus is sown on wort gelatine, the latter becomes covered with a brown felt, and is liquefied. Gemmæ are formed.

The fungus forms 5.5 vol. per cent. of alcohol in wort at 22° C. in a year. In a maltose solution it soon shows signs of fermentation, and forms 34 vol. per cent. of alcohol in eight months. In yeast water, to which 10 per cent. of dextrose has been added, it produces 2 vol. per cent. of alcohol in sixteen days at 25° C.

Mucor alternans, van Tieghem, according to Gayon and Dubourg's researches, is able to change dextrin and starch into sugars, and to ferment these substances. forms alcohol up to 4-2 vol. per cent.

It

The

Mucor corymbifer, Cohn (Fig. 61), differs considerably in appearance from the forms hitherto described. mycelium is white, later on light grey, and forms a very thick felt, the separate mycelium threads being very long. The sporangium carriers do not grow out straight, but form decumbent umbellate raceme-like branches, the ends carrying from one to twelve umbellate sporangia; below the endumbel these fruit carriers develop, in addition, a number of single, short-stalked, smaller, racemose and to some extent dwarfed sporangia. The sporangium carriers are expanded below the sporangia. The latter are colourless, pear-shaped and 10 to 70 μ in diameter. The columella is conical, broad at the top and often warty and brownish. The spores are very small and elliptical, being 3 μ long and 2 μ broad. The optimum temperature is remarkably high (37° C.). The fungus is pathogenic to man, and has been found, for example, in the eye. Wort gelatine is not liquefied by this fungus at ordinary temperature even after three months.

(2) Genus: Rhizopus, Ehrenberg.

This differs from the first genus in that the mycelium threads develop stolon-like side branches (Fig. 62, a), which grow archwise through the air, until their ends come again into contact with the substratum, when peculiar adherent

FIG. 62.-Rhizopus nigricans, Ehrenberg. a, Runners or stolons and sporangium carriers, there being usually more of the latter (3 to 5) than are shown in the figure. About . (After De Bary.) b, A columella (c) the lower part of which (a) is free; the sporangium wall grew from s. 199. (After Fischer.) c, A collapsed mushroom-like columella covered, like the previous one, with spores. 199. (After Fischer.) d, Ripe warty zygospore. 20. (After De Bary.)

organs, rhizoids, are developed. The sporangium carriers appear where these rhizoids are produced.

Rhizopus nigricans, Ehrenberg (Mucor stolonifer, Ehrenberg), is represented in Fig. 62. Two to five

sporangium carriers are found together; they are about 2 to 4 mm. long, and carry a globular blackish-brown sporangium, which encloses almost the upper half of the columella (Fig. 62, b), leaving the lower part free. The columella is well-developed and dome-shaped; after the spores have been set free it collapses into an umbrella or mushroom shape (Fig. 62, c). The spores are slightly angular and provided with ridged thickenings, being about 9 to 17 in diameter, and of a greyish-brown colour. Zygospore fructification has been observed (Fig. 62, d) on unripe gooseberries and on earth-nut cake. The suspensors are thickbodied, whilst the zygospore, which is covered with hemispherical warts, is barrel-shaped and has a diameter of from 170 to 220 μ.

This species sometimes occurs in large quantity on broken grains, and it is also productive of decay in many fruits, especially apples. J. Behrens found that this fungus secretes a protoplasm-poison, i.e., a substance which has a poisonous action on the protoplasm of the living fruit cell. It can also convert starch into sugar.

Rhizopus oryzæ, Went and Prinsen Geerligs.-The sporangia are blackish-brown with pear-shaped columellæ, and frequently a rim remains after the bursting of the sporangium wall. The size is variable, the length often being about 175 μ, and the breadth about 100 μ. The spores themselves are somewhat angular, light grey, 7 μ long and 5 μ broad. Gemmæ are produced in abundance, whilst peculiar wreath-like branchings occur on the aerial mycelia.

It changes rice starch into dextrose and is a constituent of the "raggi" mentioned above, employed in the manufacture of arrack in Java. Its probable relationship to Mucor oryzae has been already stated.

II. THE HIGHER FUNGI (MYCOMYCETES).

The mycelium is divided by septa.

A.-SAC FUNGI (ASCOMYCETES).

The fungi belonging to this division form endospores in a sporangium which is called an ascus or sac. Many such asci may be enclosed in a distinct outer envelope.

Order I.-Gymnoasceæ.

These are the simplest of the ascomycetes. The asci have no outer coating.

TRUE YEAST FUNGI (SACCHAROMYCETES).

General.

To this family belong all true alcoholic yeast fungi, on the activity of which the alcoholic fermentation industry depends; to it also belong some of the most formidable enemies with which this industry has to contend.

1.-The Saccharomycetes Distinct Fungi.

Since the year 1837, when it became evident that yeast is a vegetable growth, it has been asserted at different times by various authorities that yeast is not an independent organism, but only a separate stage of development of some higher fungus. Experimental confirmation of this was attempted, and, as the methods of that time were very imperfect, some very remarkable results were obtained. The mould fungi, especially, were accepted as the probable parent growths; this assumption was apparently strengthened by the discovery of the formation of yeast-like cells in Mucor, for here were budding cells which, like real yeast, were capable of forming alcohol. Sometimes it was believed to have been proved that Penicillium or Mucor were the parent forms, sometimes Ustilago, Aspergillus, Sterigmatocystis, Dematium, etc. Claims for the latter, especially, have been put forward quite recently.