Fungi: Their Nature and Uses

by M. C. Cooke

Of the fleshy Discomycetes the genus Peziza may be taken as the type. If the structure which prevails in this genus be brought to mind, it will be remembered that the hymenium lines an expanded cup, and that the asci are packed together, side by side, with their apices outwards, and their bases attached to a substratum of cells which form the inner layer of the receptacle. The sporidia are usually eight in each ascus, either arranged in single or double rows, or irregularly grouped together. The asci are produced in succession; the later, pressing themselves upwards between those previously developed, cause the rupture of the mature asci at the apex and the ejection of the sporidia with considerable force. When a large Peziza is observed for a time a whitish cloud will be seen to rise suddenly from the surface of the disc, which is repeated again and again whenever the specimen is moved. This cloud consists of sporidia ejected simultaneously from several asci. Sometimes the ejected sporidia lie like frost on the surface of the disc. Theories have been devised to account for this sudden extrusion of the sporidia, in Ascobolus, and a few species of Peziza, of the asci also, the most feasible one being the successive growth of the asci; contraction of the cup may also assist, as well as some other less potent causes. It may be remarked here that the sporidia in Peziza and Helotium are mostly colourless, whilst in Ascobolus they pass through pink to violet, or dark brown, and the epispore, which is of a waxy nature, becomes fissured in a more or less reticulated manner.

Fig. 67.—Sporidium of Ostreichnion Americanum.

The sporidia in Hysterium proper are usually coloured, often multiseptate, sometimes fenestrate, and occasionally of considerable size. There is no evidence that the sporidia are ever excluded in the same manner as in Peziza, the lips closing over the disc so much as to prevent this. The diffusion of the sporidia probably depends on the dissolution of the asci, and hence they will not be widely dispersed, unless, perhaps, by the action of rain.

In Tympanis, asci of two kinds have been observed in some species; one kind containing an indefinite number of very minute bodies resembling spermatia, and the other octosporous, containing sporidia of the usual type.

The Sphæriacei include an almost infinite variety in the form and character of the sporidia. Some of these are indefinite in the number contained in an ascus, although the majority are eight, and a few less. In the genera Torrubia and Hypocrea the structure differs somewhat from other groups, inasmuch as in the former the long thread-like sporidia break up into short joints, and in the latter the ascus contains sixteen subglobose or subquadrate sporidia. Other species contain linear sporidia, which are often the length of the ascus, and may either be simple or septate. In Sphæria ulnaspora the sporidia are abruptly bent at the second joint. Shorter fusiform sporidia are by no means uncommon, varying in the number of septa, and in constriction at the joints in different species. Elliptic or ovate sporidia are common, as are those of the peculiar form which may be termed sausage-shaped. These are either hyaline or coloured of some shade of brown. Coloured sporidia of this kind are common in Xylaria and Hypoxylon, as well as in certain species of the section Superficiales. Coloured sporidia are often large and beautiful: they are mostly of an elongated, elliptical form, or fusiform. As noteworthy may be mentioned the sporidia of Melanconis lanciformis, those of Valsa profusa, and some species of Massaria, the latter being at first invested with a hyaline coat. Some coloured sporidia have hyaline appendages at each extremity, as in Melanconis Berkeleii, and an allied species, Melanconis bicornis, from the United States, also some dung Sphæriæ, as S. fimiseda, included under the proposed genus Sordaria.[E] Hyaline sporidia occasionally exhibit a delicate bristle-like appendage at each extremity, as in the Valsa thelebola, or with two additional cilia at the central constriction, as in Valsa taleola. A peculiar form of sporidium is present in certain species of Sphæria found on dung, for which the generic name of Sporormia has been proposed, in which the sporidium (as in Perisporium vulgare) consists of four coloured ovate joints, which ultimately separate. Multiseptate fenestrate sporidia are not uncommon in Cucurbitaria and Pleospora, as well as in Valsa fenestrata and some other species. In the North American Sphæria putaminum the sporidia are extraordinarily large.

Fig. 68.—Ascus and sporidia of Hypocrea.	Fig. 69.—Sporidium of Sphæria ulnaspora.
Fig. 70.—Sporidia of Valsa profusa (Currey).	Fig. 71.—Sporidia of Massaria fœdans. × 400.
Fig. 72.—Sporidium of Melanconis bicornis, Cooke.	Fig. 73.—Caudate sporidia of Sphæria fimiseda.
Fig. 74.—Sporidia of Valsa thelebola.	Fig. 75.—Sporidia of Valsa taleola. × 400.
Fig. 76.—Sporidium of Sporormia intermedia.	Fig. 77.—Asci and sporidia of Sphæria (Pleospora) herbarum.

Fig. 78.—Sporidium of Sphæria putaminum. × 400.

The dissemination of the sporidia may, from identity of structure in the perithecium, be deemed to follow a like method in all. When mature, they are in a great measure expelled from the mouth of the perithecia, as is evident in species with large dark sporidia, such as exist in the genera Hypoxylon, Melanconis, and Massaria. In these genera the sporidia, on maturity, may be observed blackening the matrix round the mouths of the perithecia. As moisture has an evident effect in producing an expulsion of sporidia by swelling the gelatinous nucleus, it may be assumed that this is one of the causes of expulsion, and therefore of aids to dissemination. When Sphæriæ are submitted to extra moisture, either by placing the twig which bears them on damp sand, or dipping one end in a vessel of water, the sporidia will exude and form a gelatinous bead at the orifice. There may be other methods, and possibly the successive production of new asci may also be one, and the increase in bulk by growth of the sporidia another; but of this the evidence is scanty.