divided into Ustilagines* and Uredines. In the former, the pseudospores are mostly dingy brown or blackish, and in the latter more brightly coloured, often yellowish. The Ustilagines include the smuts and bunt of corn-plants, the Uredines include the red rusts of wheat and grasses. In some of the species included in the latter, two forms of fruit are found. In Melampsora, the summer pseudospores are yellow, globose, and were formerly classed as a species of Lecythea, whilst the winter pseudospores are brownish, elongated, wedgeshaped by compression, and compact. The Pucciniai differ primarily in the septate psendospores, which in one genus (Puccinia) are uniseptate; in Triphragmium, they are biseptate; in Phragmidium, multiseptate; and in Xenodochus, moniliform, breaking up into distinct articulations. It is probable that, in all of these, as is known to be the case in most, the septate pseudospores are preceded or accompanied by simple pseudospores, to which they are mysteriously related. There is still another, somewhat singular, group usually associated with the Pucciniai, in which the septate pseudospores are immersed in gelatin, so that in many features the species seem to approach the Tremellini. This group includes two or three genera, the type of which will be found in Podisoma.§ These fungi are parasitic on living junipers in Britain and North America, appearing year after year upon the same gouty swellings of the branches, in clavate or horn-shaped gelatinous processes of a yellowish or orange colour. Anomalous as it may at first sight appear to include these tremelloid forms with the dust-like fungi, their relations will on closer examination be more fully appreciated, when the form of pseudospores, mode of germination, and other features are taken into consideration, especially when: compared with Podisoma Ellisii, already alluded to. This family is technically characterized as, * Tulasne, "Mémoire sur les Ustilaginées," "Ann. des Sci. Nat." (1847), vii. 12-73. Tulasne, "Mémoire sur les Urédinées," "Ann. des Sci. Nat." (1854), ii. 78. § Cooke, M. C., "Notes on Podisoma," in "Journ. Quek. Micr. Club," No. 17 (1871), p. 255. Distinct hymenium none. Pseudospores either solitary or concatenate, produced on the tips of generally short threads, which are either naked or contained in a perithecium, rarely compacted into a gelatinous mass, at length producing minute spores = CONIO MYCETES. The last family of the sporifera is Hyphomycetes, in which the threads are conspicuously developed. These are what are more commonly called "moulds," including some of the most elegant and delicate of microscopic forms. It is true of many of these, as well as of the Coniomycetes, that they are only conidial forms of higher fungi; but there will remain a very large number of species which, as far as present knowledge extends, must be accepted as autonomous. In this family, we may again recognize three subdivisions, in one of which the threads are more or less compacted into a common stem, in another the threads are free, and in the third the threads can scarcely be distinguished from the mycelium. It is this latter group which unites the Hyphomycetes with the Coniomycetes, the affinities being increased by the great profusion with which the spores are developed. The first group, in which the fertile threads are united so as to form a compound stem, consists of two small orders, the Isariacei and the Stilbacei, in the former of which the spores are dry, and in the latter somewhat gelatinous. Many of the species closely imitate forms met with in the Hymenomycetes, such as Clavaria; and, in the genus Isaria, it is almost beyond doubt that the species found on dead insects, moths, spiders, flies, ants, &c., are merely the conidiophores of species of Torrubia.* The second group is by far the largest, most typical, and attractive in this family. It contains the black moulds and white moulds, technically known as the Dematiei and the Mucedines. In the first, the threads are more or less corticated, that is, the stem has a distinct investing membrane, which peels off like a bark; and the threads, often also the spores, are darkcoloured, as if charred or scorched. In many cases, the spores are highly developed, large, multiseptate, and nucleate, and sel * Tulasne, L. R. and C., "Selecta Fungorum Carpologia," vol. iii. pp. 4-19. dom are spores and threads colourless or of bright tints. In the Mucedines, on the contrary, the threads are never coated, seldom dingy, mostly white or of pure colours, and the spores have less a tendency to extra development or multiplex septation. In some genera, as in Peronospora for instance,* FIG. 40.--Rhopalomyces candidus. a secondary fruit is produced in the form of resting spores from the mycelium; and these generate zoospores as well as the primary spores, similar to those common in Algæ. This latter genus is very destructive to growing plants, one species being the chief agent in the potato disease, and another no less destructive to crops of onions. The vine disease is produced by a species of Oidium, which is also classed with Mucedines, but which is really the conidiiferous form of Erysiphe. In other genera, the majority of species are developed on decaying plants, so that, with the exception of the two genera mentioned, the Hyphomycetes exert a much less baneful influence on vegetation than the Coniomycetes. The last section, including the Sepedoniei, has been already cited as remarkable for the suppression of the threads, which are scarcely to be distinguished from the mycelium; the spores are profuse, nestling on the floccose mycelium; whilst in the Trichodermacei, the spores are invested by the threads, as if enclosed in a sort of false peridium. A summary of the characters of the family may therefore be thus briefly expressed : Filamentous; fertile threads naked, for the most part free or loosely compacted, simple or branched, bearing the spores at their apices, rarely more closely packed, so as to form a distinct common stem HYPHOMYCETES. Having thus disposed of the Sporifera, we must advert to the two families of Sporidiifera. As more closely related to the Hyphomycetes, the first of these to be noticed is the * De Bary, A., "Recherches sur les Champignons Parasites," in "Ann. des Sci. Nat." 4me sér. xx. p. 5; " Grevillea," vol. i. p. 150. Physomycetes, in which there is no proper hymenium, and the threads proceeding from the mycelium bear vesicles containing an indefinite number of sporidia. The fertile threads are either free or only slightly felted. In the order Antennariei, the threads are black and moniliform, more or less felted, bearing irregular sporangia. A common fungus named Zasmidium cellare, found in cellars, and incrusting old wine bottles, as with a blackened felt, belongs to this order. The larger and more highly-developed order, Mucorini, differs in the threads, which are simple or branched, being free, erect, and bearing the sporangia at the tips of the thread, or branches. Some of the species bear great external resemblance to Mucedines until the fruit is examined, when the fructifying heads, commonly globose or ovate, are found to be delicate transparent vesicles, enclosing a large number of minute sporidia; when mature, the sporangia burst and the sporidia are set free. In some species, it has long been known that a sort of conjugation takes place between opposite threads, which results in the formation of a sporangium.* None of these species are destructive to vegetation, appearing only upon decaying, and not upon living, plants. A state approaching putrescence seems to be essential to their vigorous development. The following characters may be compared with those of the family preceding it : FIG. 41.-Mucor caninus. Filamentous, threads free or only slightly felted, bearing vesicles, which contain indefinite sporidia=PHYSOMYCETES. In the last family, the Ascomycetes, we shall meet with a very great variety of forms, all agreeing in producing sporidia contained in certain cells called asci, which are produced from the hymenium. In some of these, the asci are evanescent, but in the greater number are permanent. In Onygenei, the receptacle is either club-shaped or somewhat globose, and the * A. de Bary, translated in "Grevillea," vol. i. p. 167; Tulasne, "Ann. des Sci. Nat." 5me sér. (1866), p. 211. peridium is filled with branched threads, which produce asci of a very evanescent character, leaving the pulverulent sporidia to fill the central cavity. The species are all small, and singular for their habit of affecting animal substances, otherwise they are of little importance. The Perisporiacei, on the other hand, are very destructive of vegetation, being produced, in the majority of cases, on the green parts of growing plants. To this order the hop mildew, rose mildew, and pea mildew belong. The mycelium is often very much developed, and in the case of the maple, pea, hop, and some others, it covers the parts attacked with a thick white coating, so that from a distance the leaves appear to have been whitewashed. Seated on the mycelium, at the first as little orange points, are the perithecia, which enlarge and become nearly black. In some species, very elegant whitish appendages radiate from the sides of the perithecia, the variations in which aid in the discrimination of species. The perithecia contain pear-shaped asci, which spring from the base and enclose a definite number of sporidia.* The asci themselves are soon dissolved. Simultaneously with the development of sporidia, other reproductive bodies are produced direct from the mycelium, and in some species as many as five different kinds of reproductive bodies have been traced. The features to be remembered in Perisporiacei, as forming the basis of their classification, are, that the asci are saccate, springing from the base of the perithecia, and are soon absorbed. Also that the perithecia themselves are not perforated at the apex. The four remaining orders, though large, can be easily characterized. In Tuberacei, all the species are subterranean, and the hymenium is mostly sinuated. In Elvellacei, the substance is more or less fleshy, and the hymenium is exposed. In Phacidiacei, the substance is hard or leathery, and the hymenium is soon exposed. And in Sphæriacei, although the substance is variable, the hymenium is never exposed, being enclosed in perithecia with a distinct opening at the apex, through which the mature spores escape. Each of these four orders must be * Léveillé, J. H., "Organisation, &c., de l'Erysiphé," in "Ann. des Sci. Nat." (1851), xv. p. 109. |