Fungi: Their Nature and Uses

by M. C. Cooke

The Coniomycetes consist of two sections, which are based on their habitats. In one section the species are developed on dead or dying plants, in the other they are parasitic on living plants. The former includes the Sphæronemei, which are variable in their proclivities, although mostly preferring dead herbaceous plants and the twigs of trees. The exceptions are in favour of Sphæronema, some of which are developed upon decaying fungi. In the large genera, Septoria, Ascochyta, Phyllosticta, Asteroma, &c., the favourite habitat is fading and dying leaves of plants of all kinds. In the majority of cases these fungi are not autonomous, but are merely the stylosporous conditions of Sphæria. They are mostly minute, and the stylospores are of the simplest kind. The Melanconiei have a preference for the twigs of trees, bursting through the bark, and expelling the spores in a gelatinous mass. A few of them are foliicolous, but the exceptions are comparatively rare, and are represented chiefly in Glœosporium, species of which are found also on apples, peaches, nectarines, and other fruits. The Torulacei are superficial, having much of the external appearance of the black moulds, and like them are found on decaying vegetable substances, old stems of herbaceous plants, dead twigs, wood, stumps of trees, &c. The exceptions are in favour of such species as Torula sporendonema, which is the red mould of cheese, and also occurs on rats’ dung, old glue, &c., and Sporendonema Muscæ, which is only the conidia of a species of Achlya. One species of Bactridium is parasitic on the hymenium of Peziza, and Echinobotryum atrum, on the flocci of black moulds.

In the other section of Coniomycetes the species are parasitic upon, and destructive to, living plants, very seldom being found on really dead substances, and even in such rare cases undoubtedly developed during the life of the tissues. Mostly the ultimate stage of these parasites is exhibited in the ruptured cuticle, and the dispersion of the dust-like spores; but in Tilletia caries, Thecaphora hyalina, and Puccinia incarcerata, they remain enclosed within the fruit of the foster-plant. The different genera exhibit in some instances a liking for plants of certain orders on which to develop themselves. Peridermium attacks the Coniferæ; Gymnosporangium and Podisoma the different species of Juniper; Melampsora chiefly the leaves of deciduous trees; Rœstelia attaches itself to pomaceous trees, whilst Graphiola affects the Palmaceæ, and Endophyllum the succulent leaves of houseleek. In Æcidium a few orders seem to be more liable to attack than others, as the Compositæ, Ranunculaceæ, Leguminosæ, Labiatæ, &c., whilst others, as the Graminaceæ, Ericaceæ, Malvaceæ, Cruciferæ, are exempt. There are, nevertheless, very few natural orders of phanerogamous plants in which some one or more species, belonging to this section of the Coniomycetes, may not be found; and the same foster-plant will occasionally nurture several forms. Recent investigations tend to confirm the distinct specific characters of the species found on different plants, and to prove that the parasite of one host will not vegetate upon another, however closely allied. This admission must not, however, be accepted as universally applicable, and therefore it should not be assumed, because a certain parasite is found developed on a special host, that it is distinct, unless distinctive characters, apart from habitat, can be detected. Æcidium compositarum and Æcidium ranunculacearum, for instance, are found on various composite and ranunculaceous plants, and as yet no sufficient evidence has been adduced to prove that the different forms are other than varieties of one of the two species. On the other hand, it is not improbable that two species of Æcidium are developed on the common berberry, as De Bary has indicated that two species of mildew, Puccinia graminis, and Puccinia straminis, are found on wheat.

Hyphomycetes.—The moulds are much more universal in their habitats, especially the Mucedines. The Isariacei have a predilection for animal substances, though not exclusively. Some species occur on dead insects, others on decaying fungi, and the rest on sticks, stems, and rotten wood. The Stilbacei have also similar habitats, except that the species of Illosporium seem to be confined to parasitism on lichens. The black moulds, Dematiei, are widely diffused, appearing on herbaceous stems, twigs, bark, and wood in most cases, but also on old linen, paper, millboard, dung, rotting fruit, &c., whilst forms of Cladosporium and Macrosporium are met with on almost every kind of vegetable substance in which the process of decay has commenced.

Mucedines, in some instances, have not been known to appear on more than one kind of matrix, but in the far greater number of cases they nourish on different substances. Aspergillus glaucus and Penicillium crustaceum are examples of these universal Mucedines. It would be far more difficult to mention substances on which these moulds are never developed than to indicate where they have been found. With the species of Peronospora it is different, for these are truly parasitic on living plants, and, as far as already known, the species are confined to certain special plants, and cannot be made to vegetate on any other. The species which causes the potato murrain, although liable to attack the tomato, and other species of Solanaceæ, does not extend its ravages beyond that natural order, whilst Peronospora parasitica confines itself to cruciferous plants. One species is restricted to the Umbelliferæ, another, or perhaps two, to the Leguminosæ, another to Rubiaceæ, two or three to Ranunculaceæ, and two or three to Caryophyllaceæ. All the experiments made by De Bary seem to prove that the species of Peronospora will only flourish on certain favoured plants, to the exclusion of all others. The non-parasitic moulds are scarcely exclusive. In Oidium some species are parasitic, but probably all the parasitic forms are states of Erysiphe, the non-parasitic alone being autonomous; of these one occurs on Porrigo lupinosa, others on putrefying oranges, pears, apples, plums, &c., and one on honeycomb. Acrospeira grows in the interior of sweet chestnuts, and we have seen a species growing within the hard testa of the seeds of Guilandina Bondue, from India, to which there was no external opening visible, and which was broken with considerable difficulty. Several Mucedines are developed on the dung of various animals, and seldom on anything else.

The Physomycetes consist of two orders, Antennariei and Mucorini, which differ from each other almost as much in habitat as in external appearance. The former, if represented by Antennaria, runs over the green and fading leaves of plants, forming a dense black stratum, like a congested layer of soot; or in Zasmidium, the common cellar fungus, runs over the walls, bottles, corks, and other substances, like a thick sooty felt. In the Mucorini, as in the Mucedines, there is usually less restriction to any special substance. Mucor mucedo occurs on bread, paste, preserves, and various substances; other species of Mucor seem to have a preference for dung, and some for decaying fungi, but rotting fruits are nearly sure to support one or other of the species. The two known species of the curious genus Pilobolus, as well as Hydrophora, are confined to dung. Sporodinia, Syzygites, &c., nourish on rotten Agarics, where they pass through their somewhat complicated existence.

The Ascomycetes contain an immense number of species, and in general terms we might say that they are found everywhere. The Tuberacei are subterraneous, with a preference for calcareous districts. The Perisporiacei are partly parasitical and partly not. The Erysiphei include those of the former which flourish at the expense of the green parts of roses, hops, maples, poplars, peas, and many other plants, both in Europe and in North America, whilst in warmer latitudes the genus Meliola appears to take their place.

The Elvellacei are fleshy fungi, of which the larger forms are terrestrial; Morchella, Gyromitra, and Helvella mostly growing in woods, Mitrula, Spathularia, and Leotia in swampy places, and Geoglossum amongst grass. The very large genus Peziza is divided into groups, of which Aleuriæ are mostly terrestrial. This group includes nearly all the large-sized species, although a few belong to the next. Lachneæ are partly terrestrial and partly epiphytal, the most minute species being found on twigs and leaves of dead plants. In Phialea the species are nearly entirely epiphytal, as is also the case in Helotium and allied genera. Some species of Peziza are developed from the curious masses of compact mycelium called Sclerotia. A few are rather eccentric in their habitats. P. viridaria, P. domestica, and P. hœmastigma, grow on damp walls; P. granulata and some others on dung. Peziza Bullii was found growing on a cistern. P. theleboloides appears in profusion on spent hops. P. episphæria, P. clavariarum, P. vulgaris, Helotium pruinosum, and others are parasitic on old fungi. One or two species of Helotium grow on submerged sticks, so as to be almost aquatic, a circumstance of rare occurrence in fungi. Other Discomycetes are similar in their habitats to the Elvellacei. The group to which the old genus Ascobolus belongs is in a great measure confined to the dung of various animals, although there are two or three lignicolous species; and Ascophanus saccharinus was first found on old leather, Ascophanus testaceus on old sacking, &c. Ascomyces is, perhaps, the lowest form which ascomycetous fungi assume, and the species are parasitic on growing plants, distorting the leaves and fruit, constituting themselves pests to the cultivators of peach, pear, and plum trees.

The Sphæriacei include a very large number of species which grow on rotten wood, bark, sticks, and twigs; another group is developed on dead herbaceous stems; yet another is confined to dead or dying leaves. One genus, Torrubia, grows chiefly on insects; Hypomyces is parasitic on dead fungi; Claviceps is developed from ergot, Poronia on dung, Polystigma on living leaves, as well as some species of Stigmatea and Dothidea. Of the genus Sphæria, a considerable number are found on dung, now included by some authors under Sordaria and Sporormia, genera founded, as we think, on insufficient characters. A limited number of species are parasitic on lichens, and one species only is known to be aquatic.

Fig. 109.—Torrubia militaris on pupa of a moth.