The stylospores of _Uredo_ are borne singly at the top of short filaments. On arriving at maturity they detach themselves. They are of a globular form, with a reddish-brown epispore, provided with little pointed prominences, and three pores at equal distances. After maturity they germinate in precisely the same manner as the stylospores of the cluster-cups. They enter only through the stomata of the epidermis. The pulvinules are identical with those which the stylospores of _Æcidium_ originate, and they also produce true spores at the end of their vegetation. No other fruit arises from them. These organs, therefore, always reproduce the same form to which they owe their origin. The result of these investigations shows that the bean rust (_Uromyces appendiculatus_), besides spermogones, possesses four sorts of reproductive organs, which all serve to propagate the species, but that one alone of them produces it in a form always identical, whilst the others present well-marked alternations of generation. Hence it is concluded that there are, I. _Spores_ which produce in germinating the promycelium, and II. _Sporidia._—These give place to a mycelium, which bears afterwards— III. _Æcidium._—Particular organs which engender stylospores, and which produce— IV. _Uredo_, the second form of the stylospores, and later spores (No. I.), which are always associated with _Uredo_ in the same pustule. The spores and stylospores of _Uredo_ come also upon the old mycelium, which has previously produced _Æcidium_. The _Uredo_ stylospores always produce _Uredo_, and true spores. ------------------------------------------------------------------------ CHAPTER IV. _MILDEW AND BRAND._