4. Algæ. Flags. In this Order the herbage is frondose, sometimes a mere crust, sometimes of a leathery or gelatinous texture. The seeds are imbedded, either in the frond itself, or in some peculiar receptacle. The barren flowers are but imperfectly known. Here we find that great natural Order, comprehended by Linnæus under one genus by the name of Lichen, the fructification of which, for the most part, consists of a smooth round disk, flat, convex, or concave, with or without an adventitious border, in the substance of which disk the seeds are lodged. In some others they are placed in powdery warts, or in fibrous receptacles. The barren flowers are supposed to be powdery also, very much like those of Jungermannia. See Engl. Bot. t. 126, and various other parts of that work, where a great number of species are figured. The whole tribe has been much investigated, and attempted to be divided into natural genera founded on habit, by Dr. Hoffmann of Goettingen, whose figures are perfect in their kind. But a more complete scheme for reducing this family
