Fungi: Their Nature and Uses

by M. C. Cooke

Fig. 22.—Pseudospores of Puccinia.

Ustilaginei.—These fungi are now usually treated as distinct from the Cæomacei, to which they are closely related.[] They are also parasitic on growing plants, but the spores are usually black or sooty, and never yellow or orange; on an average much smaller than in the Cæomacei. In Tilletia, the spores are spherical and reticulated, mixed with delicate threads, from whence they spring. In the best known species, Tilletia caries, they constitute the “bunt” of wheat. The peculiarities of germination will be alluded to hereafter. In Ustilago, the minute sooty spores are developed either on delicate threads or in compacted cells, arising first from a sort of semi-gelatinous, grumous stroma. It is very difficult to detect any threads associated with the spores. The species attack the flowers and anthers of composite and polygonaceous plants, the leaves, culms, and germen of grasses, &c., and are popularly known as “smuts.” In Urocystis and Thecaphora, the spores are united together into sub-globose bodies, forming a kind of compound spore. In some species of Urocystis, the union which subsists between them is comparatively slight. In Thecaphora, on the contrary, the complex spore, or agglomeration of spores, is compact, being at first apparently enclosed in a delicate cyst. In Tuburcinia, the minute cells are compacted into a hollow sphere, having lacunæ communicating with the interior, and often exhibiting the remains of a pedicel.

Fig. 23.—Thecaphora hyalina.

Fig. 24.—Æcidium Berberidis.

Æcidiacei.—This group differs from the foregoing three groups prominently in the presence of a cellular peridium, which encloses the spores; hence some mycologists have not hesitated to propose their association with the Gasteromycetes, although every other feature in their structure seems to indicate a close affinity with the Cæomacei. The pretty cups in the genus Æcidium are sometimes scattered and sometimes collected in clusters, either with spermogonia in the centre or on the opposite surface. The cups are usually white, composed of regularly arranged bordered cells at length bursting at the apex, with the margins turned back and split into radiating teeth. The spores are commonly of a bright orange or golden yellow, sometimes white or brownish, and are produced in chains, or moniliform strings, slightly attached to each other,[j] and breaking off at the summit at the same time that they continue to be produced at the base, so that for some time there is a successive production of spores. The spermogonia are not always readily detected, as they are much smaller than the peridia, and sometimes precede them. The spermatia are expelled from the lacerated and fringed apices, and are very minute and colourless. In Rœstelia the peridia are large, growing in company, and splitting longitudinally in many cases, or by a lacerated mouth. In most instances, the spores are brownish, but in a splendid species from North America (Rœstelia aurantiaca, Peck), recently characterized, they are of a bright orange. If Œrsted is correct in his observations, which await confirmation, these species are all related to species of Podisoma as a secondary form of fruit.[k] In the Rœstelia of the pear-tree, as well as in that of the mountain ash, the spermogonia will be found either in separate tufts on discoloured spots, or associated with the Rœstelia, In Peridermium there is very little structural difference from Rœstelia, and the species are all found on coniferous trees. In Endophyllum, the peridia are immersed in the succulent substance of the matrix; whilst in Graphiola, there is a tougher and withal double peridium, the inner of which forms a tuft of erect threads resembling a small brush.[l]

Fig. 25.—Helminthosporium molle.