Another of these “white mildews,” not only on account of its frequency of occurrence on certain plants, but also from the numerous species of phanerogamous plants on which it is found (fig. 240), may be truly designated “common” (_Erysiphe communis_, Lk.); many kinds of crow-foot, especially _Ranunculus acris_, are subject to its parasitism. It is found also on other plants of the same natural order, on the rest-harrow, trefoils, enchanter’s nightshade, bindweed, and knotgrass. There are from four to eight sporangia in each conceptacle, containing from four to eight spores (fig. 241). In this species, more especially, M. Tulasne found curious sucker-like processes developed on the threads of the mycelium (fig. 242): their office may probably be only that of attachment. Of the other species found in Britain an enumeration will suffice, since they contain no feature of interest to the microscopist; and all the members of this section are far less beautiful than those in other genera (especially _Microsphæria_). The leaves of the dogwood or cornel (figs. 245, 246) are the home of one species (_E. tortilis_, Lk.), and the burdock of another (_E. Montagnei_, Lev.). Both of these, in addition to the above, have sporangia which contain more than two spores. There are also two species in which only two spores are contained in each sporidium. One of these (_E. Linkii_, Lev.) is found on both surfaces of the leaves of the mugwort (figs. 248, 249); the other (_E. lamprocarpa_, Lev.) occurs on salsafy, scorzonera, weasel-snout, and plantain (figs. 250, 251). These complete the _Erysiphei_; but there are allied species of too much interest not to be noticed in connection with them. Three very singular fungi are found on damp straw and paper; two on the former and one on the latter. Of the species occurring on straw, the most common one is figured, natural size, in our plate (fig. 257); but from this no idea can be formed of its structure, which in some points resembles an _Erysiphe_. The conceptacles are thin and brittle, and are clothed externally with long dark-coloured branched hairs (figs. 258, 259). The conceptacle contains long narrow sporangia, each enclosing dark, almost black, lemon-shaped sporidia. For low powers this is a very interesting object. The minute structure affords no feature of popular interest. This fungus (which bears the name of _Chætomium elatum_) is common on old straw, thatch, reeds, matting, &c., resembling small brown tufts of hair, visible to the naked eye. Paper much exposed to damp will occasionally develop a similar “bristle-mould,” surrounded by a yellowish spot (_Chætomium chartarum_, Ehrb.); but it is not so common as the last. In habit and structure it is very similar (figs. 252, 253).