Amongst the parasites that prey upon the much abused berberry (which has been charged in turn with producing the mildew in corn), is one which causes the green leaves to assume a chalky appearance (fig. 229), though less conspicuously than in the maple blight. This parasite is the berberry mildew (_Microsphæria berberidis_, Lev.). In such localities as the writer has met with the berberry suffering from mildew, he has invariably found a larger proportion of leaves with the barren mycelium than of those on which the conceptacles were developed. Perhaps in other localities this may not be the case. The appendages, as will be seen on reference to our plate, differ materially from any of those to which we have referred; indeed, this genus (or sub-genus) has the most elaborate and beautiful forms in these appendages of any of the Erysiphei. A figure is given of the tip of a fulcrum from a continental species (_M. Ehrenbergii_, Lev.), not yet found in this country (fig. 233). In the berberry blight the appendages are straight at the base, but afterwards become forked, each fork being again forked, and these yet again branched in a similar manner (fig. 230); so that a complex dichotomous tip is formed to each of the appendages (fig. 231). Each conceptacle contains about six sporangia, and each sporangium contains from six to eight spores (fig. 232). The common gooseberry is also liable to a visitation from an allied species, in many respects closely similar, but differing in having the tips of the appendages more branched, and the extremities of the ultimate branchlets are not entire and attenuated, as in the berberry mildew; but divided into two toothlike processes. The conceptacles in this species contain from four to eight sporangia, each of which has four or five spores. In England, the leaves of the guelder-rose, and in France (perhaps also in this country) those of the alder, nourish a parasite belonging to this division. This “blight” possesses so much in common with others to which allusion has been made, that it will scarcely be necessary to describe it in detail. A figure of the tip of one of the appendages of the variety found on the alder is given in the Plate XI. fig. 234.