Much interest attaches to the other sub-family of _Coniomycetes_, in which the species are produced for the most part on living plants. So much has been discovered during recent years of the polymorphism which subsists amongst the species in this section, that any detailed classification can only be regarded as provisional. Hence we shall proceed here upon the supposition that we are dealing with autonomous species. In the first place, we must recognize a small section in which a kind of cellular peridium is present. This is the _Æcidiacei_, or order of "cluster cups." The majority of species are very beautiful objects under the microscope; the peridia are distinctly cellular, and white or pallid, produced beneath the cuticle, through which they burst, and, rupturing at the apex, in one genus in a stellate manner, so that the teeth, becoming reflexed, resemble delicate fringed cups, with the orange, golden, brown, or whitish spores or pseudospores nestling in the interior.[J] These pseudospores are at first produced in chains, but ultimately separate. In many cases these cups are either accompanied or preceded by spermogonia. In two other orders there is no peridium. In the _Cæomacei_, the pseudospores are more or less globose or ovate, sometimes laterally compressed and simple; and in _Pucciniæi_, they are elongated, often subfusiform and septate. In both, the pseudospores are produced in tufts or clusters _direct from the mycelium. The Cæomacei_ might again be subdivided into _Ustilagines_[K] and _Uredines_.[L] In the former, the pseudospores are mostly dingy brown or blackish, and in the latter more brightly coloured, often yellowish. The _Ustilagines_ include the smuts and bunt of corn-plants, the _Uredines_ include the red rusts of wheat and grasses. In some of the species included in the latter, two forms of fruit are found. In _Melampsora_, the summer pseudospores are yellow, globose, and were formerly classed as a species of _Lecythea_, whilst the winter pseudospores are brownish, elongated, wedge-shaped by compression, and compact. The _Pucciniæi_[M] differ primarily in the septate pseudospores, which in one genus (_Puccinia_) are uniseptate; in _Triphragmium_, they are biseptate; in _Phragmidium_, multiseptate; and in _Xenodochus_, moniliform, breaking up into distinct articulations. It is probable that, in all of these, as is known to be the case in most, the septate pseudospores are preceded or accompanied by simple pseudospores, to which they are mysteriously related. There is still another, somewhat singular, group usually associated with the _Pucciniæi_, in which the septate pseudospores are immersed in gelatin, so that in many features the species seem to approach the _Tremellini_. This group includes two or three genera, the type of which will be found in _Podisoma_.[N] These fungi are parasitic on living junipers in Britain and North America, appearing year after year