Imágenes de páginas

three quarter months at the room temperature it had formed 1 vol., after six months 3 vol., and after one year only 3.1 vol. per cent of alcohol.

The fermentability of the various species proved to be very varied. While, for instance, Mucor Mucedo did not

[graphic][merged small]

IV. FIG. 54.-Mucor Mucedo, L. I., Spores. II., Germinating spores. III., Sporangium:

2, sporangium carrier ; b, columella ; C, calcium oxalate crystals ; d, spores ; e, plasma between the spores. (After Brefeld.) 1V., a, mycelium with sporangium carriers ; s, a bursting sporangium. (After Kerner.)

reach 4 vol. per cent. of alcohol, M. erectus gave 8 vol. per cent. The facts communicated about alcohol formation in the following are from Hansen.

The powerful yeast fungi of this order show top fermentation phenomena. Emmerling found that, simaltaneously with the formation of alcohol during the fermentation, glycerine and succinic acid are formed also in about the same proportion as in Saccharomyces fermentation.

VI. Fig. 55.-Mucor Mucedo, L. V., a, Zygospore formation ; b, suspensors ; c, copula.

tion cells. VI., A complete zygospore, a; b, suspensors. (After Brefeld.)

The above-mentioned formation of spherical yeast and gemmæ has no connection with the formation of alcohol. Thus M. Mucedo, e.g., yields alcohol without possessing these organs, just as the latter are found in species which have no fermenting power. They are, however, strongly developed in all species of considerable fermenting power..


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.

FIG. 56.- Mucor racemosus, Fres. A

branched carrier with larger sporangium at the top and smaller ones on short side branches. 34. (After Fresenius.)

Fig. 57.- Mucor racemosus, Fres.

Three sporangia with transparent membrane, through which the spores are seen. 232. (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 u; 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 u long and 4 to 7 u thick, with a colourless membrane and yellowish contents. The zygospore (Fig. 55, VI.), which was found on dung, is large (90 to 200 m), spherical, brownish

Fig. 58.-Mucur racemosus, Fres. a, Part of a mycelium, the contents of which

have contracted to numerous gemmæ. 124. b, Five gemmæ together, which have germinated into small undivided sporangium carriers. 209. (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, 3:1 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.

Fig. 59.- Mucor racemosus, Fres. a, A piece of mycelium immersed in sugar

solution, separating into spherical yeast; b, Spherical yeast multiplying by budding. 179. (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 u in diameter. The spores are ellipsoidal or spherical, 5 to 8 u long and 3 to 5 u thick. The columella is pear-shaped. Zygospores occur very seldom, and are spherical, 70 to 84 u 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

« AnteriorContinuar »