In a 10 per cent. aqueous cane-sugar solution the Mucor species, like the saccharomycetes, are very tenacious of life. All the species investigated by Hansen remained alive for seven years; he proved, with regard to some species, that they were alive after more than eleven years.

b

FIG. 56.- Mucor racemosus, Fres. A branched carrier with larger sporangium at the top and smaller ones on short side branches. 3. (After Fresenius.)

FIG. 57.-Mucor racemosus, Fres. Three sporangia with transparent membrane, through which the spores are seen. ༢༠༠. (After Fischer.)

They lived, dried on filter paper, for more than four years. Mucor Mucedo, L. (Figs. 54 and 55). The mycelium is first white, later light brown. The sporangium carriers are often about 10 cm. long; the sporangium (Fig. 54, III.

and IV.) is spherical, large, with a diameter of 100 to 150 μ; it is first yellow, later grey and nearly black. The columella (Fig. 54, III., b) is a short cylinder with a dome-shaped end. The spores (Fig. 54, I.) are ellipsoidal, 7 to 12 μ long and 4 to 7 μ thick, with a colourless membrane and yellowish contents. The zygospore (Fig. 55, VI.), which was found on dung, is large (90 to 200 μ), spherical, brownish

b

a

FIG. 58.-Mucor racemosus, Fres. a, Part of a mycelium, the contents of which have contracted to numerous gemmæ. 122. b, Five gemmæ together, which have germinated into small undivided sporangium carriers. 20. (After Brefeld.)

black and with wart-like excrescences. Under special conditions (lowering of temperature, impaired nourishment or parasitical attacks) the sporangium carriers have the power of branching; the branches then often bear sporangia without columellæ, so-called sporangioles. This species does not exhibit gemma formation.

Mucor Mucedo liquefies wort gelatine when it grows on this medium. It forms in wort, after one year at the room temperature, 31 vol. per cent. of alcohol, and it appears to have then reached its maximum, In a 5 per cent. solution of maltose in yeast water it exhibited a feeble but distinct alcoholic fermentation. In a 10 per cent. solution of dextrose in yeast water it formed 0.8 vol. per cent. of alcohol after one and a half month.

The fungus is extraordinarily widely distributed in nature, and is found everywhere on manure, decomposing vegetable matter and in soil.

*

a

FIG. 59.-Mucor racemosus, Fres. a, A piece of mycelium immersed in sugar solution, separating into spherical yeast; b, Spherical yeast multiplying by budding. 120. (After Brefeld.)

Mucor racemosus, Fresenius (Figs. 56, 57, 58 and 59). -The sporangium carriers (Figs. 56 and 57) are, as a rule, branched, 2 to 3 cm. high; the sporangia (Fig. 57) spherical, brownish and 30 to 40 μ in diameter. The spores are ellipsoidal or spherical, 5 to 8 μ long and 3 to 5 μ thick. The columella is pear-shaped. Zygospores occur very seldom, and are spherical, 70 to 84 μ thick, yellowish and provided with brown, lumpy or ridged thickenings. This species displays a very abundant gemma formation (Fig. 58).

Hansen found the following temperature limits: In

wort and on wort-agar-gelatine, the maximum temperature for the development of the mycelium is 32° to 33° C., of yeast cells and gemmæ 32° C., and the minimum temperature for the mycelium and gemmæ °C. The temperature limits for the development of sporangia on wort-agar-gelatine are 31° to 32° C. and 3° to 1° C.

When Mucor racemosus is seeded on wort gelatine, its felty appearance quickly changes, the surface becoming clear and the gelatine liquefying. At the ordinary room temperature after fourteen days, it forms 13 vol. per cent. of alcohol in wort, after one year 70 vol. per cent. It ferments maltose. At 25° C. it forms, in yeast water containing 10 per cent. of dextrose, 26 vol, per cent. of alcohol after one and a half month, and at 25° C., 23 vol. per cent. of alcohol in yeast water containing 10 per cent. of cane sugar after one and a half month. This fungus is the only one of the hitherto investigated Mucor species which generates invertase, and, in consequence, is able to transform cane sugar into invert sugar and to ferment the latter.

This fungus is widely distributed and occurs particularly on plums.

Mucor erectus, Bainier, is closely related to the foregoing species, and was formerly confused with it. It does not, however, contain invertase; on the other hand, it can transform starch into a reducing sugar.

When it is sown on wort gelatine, a growth develops which is morphologically similar to M. racemosus. At the ordinary room temperature after two and a half months it forms 8 vol. per cent. of alcohol in wort, and at 25° C. 7 vol. per cent. of alcohol after the same period. In a 10 per cent. solution of dextrose in yeast water at 25° C. it forms 3:5 vol. per cent. of alcohol in fifteen days. In several respects it thus excels brewery yeast, being able to produce a higher

amount of alcohol in wort; but, as regards rapidity of fermentation, it is inferior.

Mucor oryzæ, Went and Prinsen Geerligs. The mycelium has rhizoid-like offshoots. Gemmæ (chlamydospores) are the only known organs of multiplication. This species is found in "raggi," i.e., in a mixture of rice and various organisms which is used in the manufacture of arrack in Java. It transforms the rice starch into dextrose, which is then fermented by the yeasts present. Its gemmæ cannot produce alcohol. It may possibly be identical with

0

I

FIG. 60.-Mucor spiñosus, van Tieghem. I., Sporangium carrier with sporangia. II., Sporanguim carrier with columella and loose spores. (After Gayon.)

the Rhizopus oryza to be described later, which is also found in “raggi”.

A species related to the above and employed in the

same manner is

Mucor (Amylomyces) Rouxii, Calmette, which is propagated by chlamydospores and also by means of sporangium fructification; this latter fact was discovered by Wehmer. The growths are grey, light yellow to light yellowish-brown on agar-agar, but on rice they are orange