FIG. 129.-Dematium pullulans, de Bary. I, A chain of gemmæ; three members of this (a, b, c) have produced mycelium tubes (m) on which conidia (at d) are developed. II, A chain of gemmæ developing conidia directly (at d). III, A conidium a, which has grown a mycelium thread m, on which conidia are formed; it has also formed conidia directly. IV, Conidium divided into two cells under similar conditions. V, Conidium divided into two cells developing conidia. VI, a-g, Continuous development of one and the same gemma, in a very shallow water layer with free air supply, into a double-celled, thick-walled, brown gemma rich in fat. VII and VIII, Mycelia divided up into simple, short, swollen members, which have become thick-walled gemmæ, generally much browned and furnished with large oil drops. At VIII a some of the gemmæ are seen still further divided by septa, which lie in the same direction as the axis of the thread. 49. (From Zopf's handbook.)

20*

FIG. 130.-Dematium pullulans, de Bary. Phenomenon of inter-growth. a and b show intruded mycelium threads, in 6 the thread is forming conidia. e, Conidia are being abstricted on both sides. d, A conidium in the act of budding. e, A mycelium thread has grown through the septa of two cells into a cell filled with conidia. f, Cell with four conidia strongly resembling endospores. g, One of the cells has developed conidia, a mycelium thread has grown in from the other. The remaining figures show various examples of endogenous conidium formation. e was observed at about 20° C. in a water culture about one month old; the remainder were observed in water cultures two days old at 20° and 25° C. 40. (After Klöcker and Schiönning.)

latter, and forms chains of yeast conidia at the end next to, and within the feebler cell; or, less frequently, the vigorous cell injects a longer or shorter mycelium thread (Fig. 130 a, b, e and g). The yeast conidia formed in the interior of the cell may further increase here by budding

genous conidium formations directly observed in cover glass water cultures. In the series a the development proceeded for five hours, and in 6 for twenty. four hours at 20° C. o. (After Klöcker and Schiönning.)

(Fig. 130 d), while the intrusive mycelium thread forms conidia (Fig. 130 b). When a weak cell lies between two vigorous ones, both of these latter can grow into the feeble one and form chains of yeast conidia (Fig. 131 a1-a,), or one cell intrudes a mycelium thread, while the other simply

forms conidia (Fig. 130 e). Fig. 131 shows two develg mental series of such endogenous conidia, and Fig. 132 th germination of the same. As with Oidium, the phenomen appears when young, vigorous mycelium is seeded in a litt water; when placed in wort or on moist gypsum blocks. the mycelium can also display inter-growth, but it does not take place nearly so frequently.

This fungus forms a very strong layer on nutrient liquids. v. Skerst observed the following limits of temperature for its growth in wort: Maximum 31° to 32° C., optimum 16° C., and minimum 0·5° to 2° C. In a related form Hoffmann had found that the gelatinised cell walls were stained blue by iodine. The author observed that this also occurs sometimes in the typical Dematium pullulans.

The fungus is extremely common in nature, especially on fruit. It is found in moist places in breweries.

It decolorises wort and makes it ropy. According to Lindner it clouds white beer wort; according to Wortmann it also transforms grape must into a thready gelatinous substance, which is derived from a product of the outer parts of the cell membrane. This appearance is especially marked when cane sugar is present in the liquid. In wine, however, the fungus is quickly suppressed, though not killed, by the evolution of carbonic acid. In the presence of about 8 vol. per cent. of alcohol it does not grow, but is also not killed. The so-called cork or stopper flavour of wine arises from the cork of the bottle being overgrown with various fungi, Dematium and others.

According to Wortmann, Dematium pullulans is the cause of a disease of wine grapes. The attacked grapes look like those affected with "schwarzen Brenner," but the black spots are soft, not brittle, and depressed; further they have a white, mealy spot in the middle. At this place the mycelium of the fungus breaks through the epidermis of the grapes, and the yeast buds appear. The spots often reach half round the grapes.

Dematium pullulans is one of the mould fungi which

has been repeatedly regarded as the original form of the saccharomycetes. Communications relative to this have, however, suffered the same fate as those in which the same is maintained for Penicillium, Aspergillus, Mucor, etc.; as soon as exact experiments were made, these ideas were found to be quite incorrect.

Finally, it may also be mentioned that various Ascomycetes are found, e.g., Sphærulina intermixta, Berk. and Br., and Dothidea ribesia, Pers., which can produce Dematium-like growths. If Brefeld says that the

FIG. 132.-Dematium pullulans, De Bary. Germination of endogenous conidia in wort in a cover glass preparation. The conidia (a1) swelled up after twentyfour hours and put forth germ threads (a); the same has also taken place with the uppermost two cells in the mycelium thread.

and Schiönning.)

50. (After Klöcker

species in question produce Dematium pullulans, he is in error, because these growths do not entirely correspond with the species named. Moreover, Brefeld has also been unable to produce Ascomycetes from a typical Dematium pullulans. Under certain conditions it is also found that some of the forms of Cladosporium herbarum produce Dematium-like growths.

Cladosporium herbarum, Link, is, as already mentioned, a collective name. In addition to the conidial form of Sphaerella Tulasnei, referred to on p. 283, a number of other fungi are found, which have been classed under the name Cladosporium herbarum; none of these, however, is known