It will be unnecessary to repeat what has been stated in a former chapter on spermogones. It will be remembered that these organs are found developed in connection with some of the species of the present genus, as well as with the cluster-cups, or _Æcidiacei_. They consist externally of small conical elevations, pierced at the apex, which contain minute, cellular, linear bodies called spermatia, invested with a kind of mucous substance, that over-flows with them from the orifice of the spermogone, like lava from the crater of a miniature volcano. The rust in company with which they have been found most plentifully, is that which covers the under surface of the leaves of the commonest of all thistles (_Cnicus arvensis_). The external form of one of these spermogones is figured Plate VII. fig. 153. The rust possesses, when fresh, a peculiar odour, which is said to resemble that of orange-flowers; whence was derived its name of “sweet-smelling rust” (_Trichobasis suaveolens_, Lev.). M. Tulasne writes:—“With respect to this species, it is, in my opinion, but the first form of a _Puccinia_, analogous to _P. Compositarum_, D.C.: the spermogones with which it is mixed being very abundant, it ought to be placed with that _Puccinia_. I should, perhaps, retain some doubts upon the legitimacy of this relationship, if it had not been my fortune to meet on another species of the same kind (_Puccinia Anemones_, P.) spermogones perfectly characterized, and in which the colour, habit, and position would not allow me to hesitate an instant in attributing them to the _Puccinia_.” In this species of rust the whole under surface of the leaf is covered with a purplish-brown dusty coating of the spores, from the numerous pustules which are produced (Plate VII. fig. 151). The plants, when attacked, have a paler and more sickly appearance; the leaves have a tendency to fold backwards at their margins, and thenceforth their growth seems to be determined. Sowerby, in his “British Fungi,” says:—“Two or three sorts of flies are occasionally found dead on this plant at the time of the fungus being upon it, which is after wet weather in the summer, or early in autumn; being apparently tempted by its flavour, they over-eat themselves, or else are destroyed by some poison.” This rust has spores resembling, in general characters, those of the yellow-spored series Plate VII. fig. 152). We have not thought it necessary to give figures of many species, partly on account of the uncertainty existing in many minds whether they ought to be regarded as species, and whether they will long claim a place in the British Flora; and partly on account of the similarity which exists between them, at least so far as they are of interest to the microscopist only.