In some instances, as in _Rœstelia cornuta_, which is found on the leaves of the mountain-ash, the cups are produced on the lower, but the spermogones almost exclusively on the upper surface.
The spermogones of _Peridermium Pini_ are white, few in number, and are developed, not only in the spring, but sometimes reappear in the autumn upon the same leaves that produced them at the commencement of the year.
In such instances as those of the _Æcidium_ of the spurge, and also the goatsbeard, in which the cluster-cups are arranged in no appreciable order, the spermogones are scattered amongst them, and even in some instances appear on different leaves. The spermogones are common on the wood spurge in spring, scattered over both surfaces of the leaves before the cluster-cups make their appearance, and gradually these latter are developed amongst them, commencing from the apex of the leaves and proceeding in the order of their development towards the base. In this instance the spermogones are bright yellow, as are afterwards the cups and spores of the _Æcidium_. In most instances the appearance of the spermogones precedes that of the sporiferous organs, but the latter follow sufficiently speedy for perfect development before the decadence of the spermogones takes place.
After the expulsion of the spermatia and the fluid which accompanies them, the whole mass dries up; and where many spermogones have been clustered together in the same spot a brown homogeneous crust is formed upon the epidermis; where they are produced singly, a brownish incrustation is visible about the mouth of each spermogone.
Re-agents applied to the spermogones whilst in full vitality indicate the presence of a considerable amount of a protein substance, which, with sugar and sulphuric acid, produces a deep purple red colour.
From what we have already stated of the method of occurrence of these organs, the following is the only order, apparently, preserved in their development, although no definite rules can at present be affirmed. The spore spots of cluster-cups are generally found upon the under surfaces of the leaves on which they are produced, and the spermogones are most numerous on the upper. When both the cluster-cups and the spermogones appear in the same group on the same surface, the spermogones commonly occupy the centre, and the cups are arranged in a circular manner about them. In other, and fewer instances, both organs stand together indiscriminately upon the same surface.