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sisting of branched mycelium threads, which grow up partly from the base of the ascogonium and partly from the mycelium. This growth becomes gradually denser and harder ; the ascogonium enlarges and its branches force themselves in all directions between the middle growth, consisting of thinner-walled cells. When such a sclerotium, fully ripe, is placed on damp filter paper, the ascogenous threads separate and push out thick side branches, the links of which finally change into asci. At the same time thin threads develop from the ascogenous hyphæ which penetrate into the sterile growth and dissolve it up. The foodstuffs thus
Fig. 108.- Penicillium glaucum, Link. A, Conidiophore. B, Sexual organs. C.
Beginning of sclerotinm (a, ascogenous hyphæ; b, sterile threads). D, Very young sclerotium in section.
obtained are taken by the fine threads to the ascogenous hyphæ. Finally, the dissolving process progresses so far that only the peripheral rind remains, while the inside appears filled up with spore masses. Perithecium formation takes place, according to Brefeld, only by abundant nourishment on bread. The ascospores, eight in each ascus, are yellowish, elliptical, 5 to 9 u long and 4 to 7 u broad.
The cardinal temperatures for the growth vary, according to Thiele, with the substratum. Thus the fungus is said to grow at 35° to 36° C. if glycerine and sodium formate
are present, whereas 4 per cent. of grape sugar impedes growth at a temperature above 31° C. The temperature minimum is, on the contrary, unchanged by the substances named.
Pasteur states that the conidia are killed if exposed for half an hour to a temperature of 127° to 132° C.; at 119° to 121° C. they retain life. According to Lesage they are killed somewhat quickly by alcohol vapour, the times being six days, nearly one day, and two hours when subjected to the vapour from 22:5 per cent., 45 per cent., and 90 per cent. solutions of alcohol respectively.
P. glaucum contains diastase and maltase (Bourquelot), also a ferment which inverts cane sugar, and emulsin (Gérard). The diastatic action is, however, weakened if the content of the substratum in sugar increases ; in a 10 to 15 per cent. cane sugar solution this fungus forms no diastase (Katz). It, further, breaks up tannin into gallic acid and glucose (v. Tieghem) and mandelic acid into its two optically active isomers, using the levo-acid in building up the cells (Lewkowitsch); this is said by Pfeffer, however, to be dependent for the most part on external influences. Under certain conditions it is said to be capable of forming mannite as the product of decomposition (Muntz). Rotten grapes with Penicillium growth may therefore produce a sick wine containing mannite. Calcium oxalate is deposited in the perithecia.
Mention of its occurrence on barley and malt, and its injurious action on wort and beer is to be found on p. 273.
When it is present in grape must, fermentation is much delayed. Müller-Thurgau is of the opinion that the cause of this is the formation of injurious substances, for fermentation is also restrained when the fungus is removed from the liquor before the addition of the yeast. Miyoshi found that it forms a specific protoplasm poison, and J. Behrens has shown experimentally its poisonous action on yeast as regards both
fermentation and fermentative power. By a stronger nutrition of the yeast, e.g., by addition of peptone to the nutrient solution, he succeeded in stopping this injurious action. The fungus causes the mouldy taste in wine, as well as a cork or stopper taste, by growing through the cork of the bottle (Wortmann). Like Aspergillus, it attacks hops, colouring them brown.
P. glaucum is very widespread in nature, and the air is full of its conidia. It is, therefore, one of the most dangerous guests in the laboratory, all the more as it only requires a very small quantity of nutriment for the support of life; but it also requires a certain amount of moisture. With regard to temperature, too, it is not particular; it thrives well at about 0°. It is frequently met with on fruit, kernel as well as stone fruit, and it is said to be able to penetrate the uninjured surface of grapes. Wehmer found it in herring pickle, and isolated it by means of plate cultures on nutrient gelatine, containing 10 per cent. of common salt, on which substratum it grew easily.
It betrays its presence by its characteristic smell.
Order III.—Sphæriacea. The fungi belonging to this order have, with one exception and contrary to the Perisporacea, an opening in the dark-coloured perithecium. Conidia fructification takes place. This order includes a very large number of parasitical species.
Genus : Sphærella, Cés. and de Not. The almost spherical perithecia are set in the epidermis or in the uppermost layers of the web of the host and end in a simple, uncommon, papilla-shaped opening of fine skin-like consistency. The asci are connected in bundles ; the spores are two-celled and colourless (seldom coloured).
Sphærella Tulasnei, Janczewski (Fig. 109), forms darkcoloured perithecia, frequently pear-shaped (Fig. 109 7), 0:3 to 0:4 mm. long and 0.15 to 0·20 mm. in diameter. At its surface, chiefly at the neck, numerous mycelium threads are often found which develop conidiophores (Fig. 109 7). The perithecia contain asci with eight spores (Fig. 109 8, 9), of which the topmost is larger than the others; its size is 28 u in length and 6:5 u in diameter.
The conidial form is one of those fungi which were formerly called Cladosporium herbarum, Link (Fig. 109 1, 2, 3). This name has been used, like Penicillium glaucum, Aspergillus glaucus and others, to designate several fungi. It is now impossible to say which species Link meant. Common to all is the mycelium, at first clear like water, and later olive green or brown, which sends out conidiophores that abstrict brown conidia often many-celled. The form named Cladosporium herbarum by Janczewski corresponds with that usually so called (Fig. 109 1-4). He describes the conidia as oval, either undivided or 2 to 5 celled (Fig. 109 5). In the largest varieties they are 25 u long and 10 u broad; in the smaller forms they are only half as large. Their cell wall is olive brown, often warty, but smooth in the smaller variety. The young mycelium is uncoloured, and only assumes the olive brown colour gradually. For the rest, the appearance may be made out from Fig. 109.
Janczewski showed, by experiments with seedings on barley and rye, that this fungus is the conidial form of the above Sphærella Tulasnei. It grows here as a saprophyte, not as a parasite. As soon as the conidia were brought to germination on nutrient gelatine, a piece of the gelatine with germinating conidia was placed on a cut rye leaf which was kept in a very damp atmosphere. The mycelium then grew up; as soon as the point of the latter reached one of the stomata in the leaf, it forced its way through this into the leaf,
Fig. 109.--Spharella Tulasnei, Janczewski. 1, 2, 3. The conidial form Clado
sporium herbarum, Link. 250. 4. The same growing out through a stoma in the rye leaf sheath. 335. 5. Conidia. sp. 6. Sclerotium with a mycelium thread in a rye leaf sheath. 492. 7. Perithecia with conidiophores. 49. 8. Longitudinal section of perithecium containing two asci with endospores. 322. 9. Ascus with ripe endospores. 40.9. 10. Conidiophores developed
m endospores. 199. (After Janczewski.)