Experience has also taught us that many fungi flourish in proportion to the wetness of the season, or dampness of the locality. A wet year is always exceedingly prolific in fungi, and a dry season correspondingly barren, at least in many kinds, whilst others, as the experience of 1864 has convinced us, are exceedingly common. In a field or wood the mycologist reaps his richest harvest of mycological specimens in the lowest and dampest spots, in swamps, ditches, and ill-drained nooks. This is a fact worth knowing as much by the farmer as the amateur botanist in search of specimens for his herbarium. One of the most unmistakable species of “smut” is that which infests the goatsbeard, on which we have already described an _Æcidium_. Generally about the same time as the cluster-cups make their appearance on the leaves, some of the unopened flower-heads of this plant will be found considerably altered in appearance by the shortening of the segments of the involucre, and at length by the whole inflorescence being invested with a copious purplish-black dust. If, by any means, the lobes of the involucre are any of them separated, the enclosed dust escapes, blackening the fingers and clothing of the collector, as if it were soot (Plate V. fig. 92). A little of this dust submitted to the microscope will be found to consist of myriads of small globose spores, nearly uniform in size and shape; and if a higher power be employed, each of these will appear to have a papillose or minutely granulated surface. The florets, dwarfed in size and contorted, or the remains of them, are embedded in the mass of spores (fig. 93), and if one or two of these are removed and placed under a good one-inch objective, every part will be found covered with adhering spores, to the apparent exhaustion of its substance. Of course, the florets are never developed when subjected to the attack of “smut.” The whole plant assumes a faded, sickly appearance, even before the spores are fully ripened. We would recommend our readers, if they collect one of the infected flower-heads, to put it into a box or paper by itself, for if placed in the box with other specimens it will so sprinkle them with its black powder as to render them nearly useless for microscopic examination: everywhere the microscope will detect, where the unaided eye failed to recognize a trace, the ubiquitous spores of _Ustilago receptaculorum_ (Plate V. fig. 94). In the fenny districts of the eastern counties a species of “smut” called _Ustilago typhoides_ attacks the stems of reeds, forming thick swollen patches of several inches in length (fig. 128), sometimes occupying the whole space between two joints or nodes, and lying beneath the sheath of the leaves. The spores in this species are larger than in the species which attacks the culms of grasses in a similar manner (Plate VI. fig. 129).