The cottony tufts of white mould, which were the first to appear, had an abundant mycelium, but the erect threads which sprang from this were for a long time sterile, and closely interlaced. At length fertile threads were developed in tufts, mixed with the sterile threads. These fruit-bearers were shorter and stouter, more sparingly branched, but beset throughout nearly their whole length with short patent, alternate branchlets. These latter were broadest towards the apex, so as to be almost clavate, and the extremity was beset with two or three short spicules. Each spicule was normally surmounted by an obovate spore. The presence of fertile threads imparted the ochraceous tint above alluded to. This tint was slight, and perhaps would not have been noticed, but from the close proximity of the snow-white tufts of barren threads. The fertile flocci were decumbent, probably from the weight of the spores, and the tufts were a little elevated above the surface of the matrix. This mould belonged clearly to the _Mucedines_, but it hardly accorded well with any known genus, although most intimately related to _Rhinotrichum_, in which it was placed as _Rhinotrichum lanosum_.[R] The white mould having become established for a week or two, small blackish spots made their appearance on the paper, sometimes amongst thin patches of the mould, and sometimes outside them. These spots, at first cloudy and indefinite, varied in size, but were usually less than a quarter of an inch in diameter. The varnish of the paper was afterwards pushed off in little translucent flakes or scales, an erect olivaceous mould appeared, and the patches extended to nearly an inch in diameter, maintaining an almost universal circular form. This new mould sometimes possessed a dirty reddish tint, but was commonly dark olive. There could be no mistake about the genus to which this mould belonged; it had all the essential characters of _Penicillium_. Erect jointed threads, branched in the upper portion in a fasciculate manner, and bearing long beaded threads of spores, which formed a tassel-like head, at the apex of each fertile thread. Although at first reminded of _Penicillium olivaceum_, of Corda, by the colour of this species, it was found to differ in the spores being oblong instead of globose, and the ramifications of the flocci were different. Unable again to find a described species of _Penicillium_ with which this new mould would agree, it was described under the name of _Penicillium chartarum_.[S]