Page:An introduction to physiological and systematical botany (1st edition).djvu/528

 498 its seeds being dispersed under the cuticle throughout the membranous or gelatinous substance of the frond; Fucus, t. 1066—1069, &c., whose seeds are collected together in tubercles or swellings, of various forms and sizes; and Conferva, of which the 24th and 25th volumes of ''Engl. Bot.'', more especially, show various specimens. This last genus is commonly known by its capillary, and, for the most part, jointed frond. The seeds of some species are lodged in external capsules or tubercles; of others in the joints of the frond; and hence the ingenious Dr. Roth has formed a genus of the former, called Ceramium. His Rivularia, ''Engl. Bot. t. 1797—1799, is perhaps more satisfactorily separated from Conferva, as we trust is Vaucheria, t. 1765, 1766, a fresh-water genus named after M. Vaucher'' of Geneva, who has published an elaborate and faithful microscopical work on Fresh-water Confervas. The submersed Algæ in general are merely fixed by the roots, their nourishment being imbibed by their surface. Many of them float without being attached to any