Plants of the pea and bean tribe are liable to be attacked by one of these rusts, and in this instance the spores are so characteristic that no one could well confound them with any other. Externally it appears as an irregular brownish pustule, breaking through the epidermis and filled with an impalpable powder, not unlike a pinch of “brown rappee” snuff. The spores are ovoid, with a very long peduncle, whence its name (_Uromyces appendiculata_). It appears on a great variety of plants, but from the peculiarity of the spores Plate VII. fig. 150), is easily recognized. Our figure represents it on the leaf of a vetch (Plate VII. fig. 149). Almost at the commencement of this volume (Chap. III.) we had occasion to refer in detail to some experiments made by De Bary on the spores of this species. In the remarks then made occurs a recommendation of reperusal, which would obviate any repetition here. An allied species, and a beautiful one, is to be found on the stinking iris (_Iris fœtidissima_), and another on the under surface of the leaves of primroses. The pilewort (_Ranunculus ficaria_) we have already seen attacked by one species of microscopic fungi, and we have now to record the occurrence of another. Some plants appear to be destined both alive and dead to become the prey of others. The common nettle, for instance, as if in retribution for the annoyance it often occasions on account of its stinging propensities, has not less than twenty different species of minute fungi, to say nothing of coleopterous and lepidopterous insects, which make a home, sometimes upon its green leaves, and sometimes on its dead stems. We might almost state that it has a flora and a fauna of its own. The pilewort, too, has many foes; but these are fewer in number, and mostly attack the living plant. The cluster-cups have been already noticed; some do not fall within the limits of this volume, but one, which is found in May and June, belongs to the present genus. It appears like a purplish-brown powder bursting through blistered spots on the leaves and footstalks Plate VII. fig. 156). The spores are small, and are, of course, provided with pedicels Plate VII. fig. 157).