Sedges are subject to the attacks of a rust much resembling the corn rust. When it occurs on some species of Carex, the upper surface of the leaf has corresponding pale spots, and the pustules themselves are surrounded by a yellowish margin. This species (Trichobasis caricina) is far from uncommon ([Plate VIII.] figs. 170, 171). The sedge-like plants belonging to the genus Luzula have also their own species of rust (Trichobasis oblongata), the spores of which are deeper in colour than in the sedge rust ([Plate VII.] figs. 158, 159).
Amongst the remaining species of Trichobasis (the reader must pardon our using the generic name, as we have no equivalent), that found on the leaves of various composite plants is the most common (Trichobasis Cichoracearum, Lev.). It occurs on some thistles, on the saw-wort, dandelion, several species of hawkweed, and similar plants. The pustules are small and more diffused than in the species found on Cnicus arvensis, and they as often appear on the upper as on the lower surfaces of the leaves.
On umbelliferous plants three species are recorded; one with yellow spores (Trichobasis Petroselini, B.); another with a blistered habit, and brown, ovate, or oblong spores (T. Umbellatarum, Lev.); and a third with tawny, obovate, or egg-shaped spores (T. Heraclei, B.), which is found solely on the cow-parsnip. The species of Puccinia corresponding to some of these species of Trichobasis are known, but, in other cases, probability, or speculation if you please, occupies the place of knowledge.
During the month of September, 1864, it was our good fortune to spend a week in revisiting the scenes of our boyhood, and exploring the minute botany of one of the marshy districts of East Norfolk. One day of the seven, memorable to us for the discovery of three specimens of a large Boletus (B. cyanescens),[[7]] not found, to our knowledge, since the days of Sibthorpe, was further enriched by a species of Trichobasis, new to Britain, and apparently uncommon on the Continent. This rust was found on the leaves of the “grass of Parnassus” (Parnassia palustris) on a narrow strip of marsh near Irstead church. It was sought in vain elsewhere. The leaves were scarcely changed in appearance, except by the presence of the pustules. There were no discoloured spots, but the pustules appeared sometimes plentifully, more often scattered, on both surfaces of the leaves: they were small, of a bright brown, with oval spores; the latter were, in their early stages, shortly stalked. We have called this species Trichobasis Parnassiæ. It is possibly the same as published by Westendorp in his “Herbier Cryptogamique Belge” as Uredo Parnassiæ, but we know of no copy which we can consult, and have failed in discovering any other species to which we can refer it. It is certainly a Trichobasis and not an Uredo, according to the present limitation of the latter genus.
[7]. Two of these specimens were found at the bottom of a hedge-bank, amongst grass, by the side of the road leading from Neatishead-street to Irstead Rectory, and the third in a similar position by the Norwich road, two hundred yards from the turning which leads to Neatishead-street.
Although the evidence against the retention of the species of Lecythea (as the genus is named) amongst Fungi as true species, on the ground of di-morphism, is even stronger than against the group just illustrated, we cannot pass them altogether in silence, especially in a popular treatise. Those who are residents in town, and yet possess their little plot of garden-ground, with only two or three pet roses, may have had the misfortune of seeing them smothered with a yellow blight. This golden visitation, unwelcome as it is, may afford a subject for the microscope, and for a small space in this chapter. At first there will not appear to be any important difference between the spores of the yellow series of the last genus and those of the present; but a closer examination will reveal one important distinction, viz., the presence of colourless elongated, abortive spores. The species are not so numerous by half as those of Trichobasis, even when three anomalous forms are included, which species are included by some mycologists in two other genera. One very common rust of this group has already been alluded to ([Plate II.] fig. 37), and which is known botanically as Lecythea Rosæ. A similar one is found on the bramble, and another on the burnet. All these three species are produced at first on spots which are afterwards more or less occupied by the long, many-celled spores of the dark brown brands called Aregma or Phragmidium, between which and the simple yellow spores of the rust almost every intermediate form may often be found in the same pustule. Thus, from the same mycelium as that of the rose rust, the rose brand is afterwards developed; whilst from the nidus of the bramble rust ([Plate III.] fig. 40) the bramble brand is also at length produced; and the successor to the burnet rust ([Plate III.] fig. 31) is the burnet brand. Besides these, a rust belonging to the same genus may be found on the leaves of the poplar, the spurge, and the common valerian, and two or three species on willows. It can scarcely have escaped notice, that the goat-willow is almost constantly afflicted with a rust on the under surface of the leaves ([Plate VIII.] fig. 160). This species will again come under notice as the summer spores of a truly dimorphous species.
One of the rusts separated by some botanists from this genus is found (possibly most commonly) on the leaves of the raspberry; but during the past autumn we have met with it plentifully on the upper surface of the leaves of one or two species of bramble, and have never seen it growing on the raspberry, although in all descriptions of the species that is stated to be its habitat. Even to the naked eye this is so distinct, that no one could well confound it with any other. It appears very late in the autumn, and the spots are scattered at some distance apart from each other ([Plate VIII.] fig. 162); each spot or pustule forming a ring ([Plate VIII.] fig. 163 enlarged) encircling a cluster of spermogones which occupy the centre.
Another rejected species (Lecythea Lini, Lev.) occurs on the little purging flax (Linum catharticum), forming small pustules on the leaves ([Plate VIII.] fig. 165); these burst irregularly, and remain surrounded by the remains of the ruptured epidermis ([Plate VIII.] fig. 166). The yellowish spores are subglobose ([Plate VIII.] fig. 167), and in the first instance concatenate, or chained together like a necklace, which circumstance has been taken advantage of to place it, with one or two other species, in a separate genus.
We cannot claim for the species brought into notice in the present chapter any attractive features resulting from singularity of form, complexity of structure, or delicate tracery, whereby they might commend themselves to mere “searchers after curiosities,” or be recommended from friend to friend as “sensation” objects for the microscope. They do possess an interest and a value, but such as would not be appreciated by those who seek to pass an idle half-hour by gazing at some new thing.