3. _Chaetophoraceæ_.--Plants growing in the sea or fresh water, coated by gelatinous substance; either filiform or a number of filaments being connected together constituting gelatinous, definitely formed, or shapeless fronds or masses. Filaments jointed, bearing bristle-like processes. Fructification: zoospores produced from the cell contents of the filaments; resting spores formed from the contents of particular cells after impregnation by ciliated spermatozoids produced in distinct antheridial cells. Coleochætæ. 4. _Confervaceæ_.--Plants growing in the sea or in fresh water, filamentous, jointed, without evident gelatine (forming merely a delicate coat around the separate filaments) Filaments very variable in appearance, simple or branched; the cells constituting the articulations of the filaments more or less filled with green, or very rarely brown or purple granular matter; sometimes arranged in peculiar patterns on the walls, and convertible into spores or zoospores. Not conjugating. 5. _Zygnemaceæ_.--Aquatic filamentous plants, without evident gelatine, composed of series of cylindrical cells, straight or curved. Cell contents often arranged in elegant patterns on the walls. Reproduction resulting from conjugation, followed by the development of a true spore, in some genera dividing into four sporules before germinating. 6. _OEdogoniaceæ_.--Simple or branched aquatic filamentous plants attached without gelatine. Cell contents uniform, dense, cell division accompanied by circumscissile debiscence of the parent cell, producing rings on the filaments. Reproduction by zoospores formed of the whole contents of a cell, with a crown of numerous cilia; resting spores formed in sporangial cells after fecundation by ciliated spermatozoids formed in antheridial cells. 7. _Siphonaceæ_--Plants found in the sea, fresh water, or on damp ground; of a membranous or horny byaline substance, filled with green or colorless granular matter. Fronds consisting of continuous tubular filaments, either free or collected into spongy masses of various shapes. Crustaceous, globular, cylindrical, or flat. Fructification: by zoospores, either single or very numerous, and by resting spores formed in sporangial cells after the contents have been impregnated by the contents of autheridial cells of different forms.