It is unnecessary here to refer to other allied species of _Æcidium_, except one to be presently noticed, since we have, at the end of the volume, enumerated and given descriptions of all the species hitherto found in Britain. Suffice it to say that the Buckthorn cluster-cups on the alder buckthorn (_Rhamnus frangula_), is usually very common in the Highgate and Hornsey woods, and on the common buckthorn (_Rhamnus catharticus_) in the neighbourhood of Dartford, in Kent. That on the honeysuckle we have found but very rarely. On the gooseberry and red-currant leaves, commonly in some years and rarely in others; whilst a few of those described we have never collected. The species on different composite plants is subject to great variation, and on most may be found in the autumn; one variety only, on the leaves of _Lapsana communis_, we have met with in the spring. Very few years ago farmers generally believed that the cluster-cups of the berberry (_Berberis vulgaris_), were productive of mildew in corn grown near them; this opinion even received the support of Sir J. Banks, but no fungi can be much more distinct than those found on corn crops and this species on the leaves of the berberry. In this instance the cups are much elongated, and cylindrical, the clusters vary much in size, and the spots on the upper surface of the leaf are reddish, bright, and distinct. The teeth are white and brittle, and the orange spores copious (Plate I. figs. 7-9). There are scarcely any of the epiphyllous fungi forming equally handsome or interesting objects for low powers of the microscope, than the genus to which attention has just been directed; and they possess the advantage of being readily found, for that locality must be poor indeed which cannot furnish six species during the year. We have found half of the number of described species within little more than walking distance of the metropolis, within a period of little more than three months, and should be glad to hear of the occurrence of any of the rest.