Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/869

 FUNGUS 833 Suborder III. 6 asteromycetes. The receptacles of the Gas eromycetes are angiocarpous. They consist of an outer peridium enclosing masses of tissue which bear the hymenia. The basidia often bear as many as eight spores, which are ultimately liberated by the bursting of the peridium, either simply or by the development of special masses of tissues. The peridium of Phallus resembles the velum universal^ of the Agaricini in its mode of enveloping the receptacle, and the appearance it presents after bursting. Within this volva is a gelatinous stratum, then an inner peridium, then the hymenium. The bursting of the peridium or volva is caused by the elongation of a stalk on which the hymenium is elevated in a kind of pileus as in the Agaricini. In Batarrea there also occurs a universal volva, and the hymenium is similarly elevated, but the plant in this case is of a woody consistence, and spiral vessels are found in the stalk. In Clathrus the receptacle is in the form of a globular net. In Lycoperdon, Hymenogaster, and Nidularia the hyme nium remains unelevated, and the spores are liberated by the simple bursting of the peridium. Order IV. ASCOMYCETES. The characteristic form of re production of the A scomycetes is by scos/&amp;gt;o?-es formed within asci by free cell-formation. Other generations in the cycle of development form stylospores in special conceptacles called pycnidia, and conidia borne on conidiophores. The receptacles on which the ascospores are produced arise as the result of the union of sexual organs, which takes place on the mycelium. The receptacles vary very much in size and form throughout the order. Suborder I. Discomycetes. The sexual organs of this suborder are formed on the mycelium and are called the carpogonium (female) and the pollinodium (male). As typical of the rest of the order the life-history of Ascobolus furfuraceus, as described by Janczewski may be chosen. The pollinodium and carpogoniumareboth composed of a series of short crooked cells, in the former case much thinner than in the latter. The pollinodium em braces the more remote end of the carpogonium, which is at this stage sausage-shaped, and so fertilizes it. After fer tilization one of the cells of the carpogonium (usu ally near the increases and becomes globular. It is called the ascogonium. From it pro ceed ascogenous hyphae on which the asci arise. The asci are flask-shaped, the base being the narrow portion, and within them the asco spores, 8 in number, are formed by free cell-formation. Between the asci, and borne on the ascogenous hyphoc, are more or leas numerous paraph&amp;gt;/ses which are generally regarded as abortive asci, but may serve (as Boudier affirms they do) to assist in some way the dehiscence of the asci. The hyphae of the mycelium on which the sexual organs are borne produce a dense mass of pseudo-parenchyma, which surrounds the carpogonium and forms the sterile part of the fructification. Sexuality was first discovered in the Discomycetes by Professor De Bary in the case of Peziza confluens, which, though it differs in details from that described as occurring in Ascobolus, agrees in all essential details with it. middle) ~ir,.5.As&amp;lt;-obo?usfurfvraceus. Diagrammatic stction of the fructification (after Jan czewski). m, mycelium; c, carpogonium; /, pollinodium ; s, ascogenous filaments; a, asci ; r, p, the sterile tissue from which the paraphyses h spring. Certain species of Peziza?, the mycelium of which is ex- Fuckeliana by Professor De Bary. In it conidia are pro duced by the mycelium before the sclerotia. The sclerotia, which are formed without the occurrence of any sexual pro cess, so far as has been observed, consist of densely packed liyphae enclosed by a pseudo-parenchymatous rind. Some times these germinate shortly after their formation, and produce a mycelium which bears conidia again ; but if germination be delayed for a mouth or two, the character istic basin-shaped hymenium of Peziza, with asci and asco spores, is formed. Spermatia are found in this as in other orders. They are borne in spermogonia, similar to those of the Uredinea?, and were long believed to be incapable of germination. M. Cornu, however, has recently stated that he caused them to germinate under artificial conditions, and to produce a mycelium like the conidia. In Peziza arid the genera closely allied to it, the asco genous receptacle is basin-shaped, with the hymenium on the inner surface of the basin ; but in other genera it takes the form of clubs or stalks of considerable size with the hymenium on the outer surface (as in Geoglossum, Spathu- laria, Helvetia, Morchella, &amp;lt;fcc.). The species of Morchella and Helvella are, as a rule, esculent ; but none of the other Discomycetes have ever ob tained any reputation in this direction. Suborder II. Erysiphece. In this suborder the species follow two types in their mode of sexual reproduction, viz., Erysiphe and Eurotium. R FIG. 6. Development of Eurotium repent (after De Bary). A. small portion of mycelium with conidiophore r, and young ascogonium at. JB, I he spiral asco- gonium (at), with the antheridium (p). D, the same, beginning to bo sur rounded by the hyphse forming the ptrithecium wall. D, the piTithccium. E,F, sections of young pcrithccia:, parietal cells; / pscudo-pnrer.chyma; at, ascogonium. G, an ascus. II, an ascospore. The mycelium of Erysiphe creeps over the surface of its host plant, through the epidermis of which it sends down numerous haustoria. Both the conidia and the sexually produced fruits are borne on the same mycelium. The conidia occur in vertical order at the end of unbranched conidiophores. These conidia reproduce the mycelium directly. The mode of sexual reproduction resembles that of the Discomycetes. The carpogonium is more or less globular in shape, and is fertilized by a pollinodium of one or more branches. The carpogonium is at first represented IX. 105
 * ensively reproduced by conidia, undergo a resting state in
 * he form of a sclerotium. This was first observed in Peziza