The typical genus (_Rhodymenia_) contains two red, membranous weeds, the commoner of which is _R. palmata_ (Plate VIII.), so common on the Scottish and Irish coasts, where it forms an important article of diet, and is known as the Dulse or Dillisk. It is also widely distributed over the English coasts. Its broad, fleshy fronds are divided into finger-like lobes, and are either sessile or supported on a stalk that proceeds from a small discoid root. The frond is very variable in form, being sometimes divided into very narrow segments, and sometimes quite undivided. One variety has a number of small stalked leaflets on its margin (see Plate VIII.); and another is very narrow, with wedge-shaped irregular lobes. _R. palmetta_ is a smaller and less common species that grows on rocks and large weeds in deep water. The tetraspores form crimson patches on the tips of the lobes. _Maugeria_ (_Delesseria_) _sanguinea_ (Plate VIII.) is a large and beautiful weed, of a blood-red colour, that grows in the lower rock pools or beyond low-water mark, under the shade of high rocks or hidden by the olive tangles. Its frond is thin and membranous, with a well-defined midrib. The spores are contained in globular stalked conceptacles, usually on one side of the midrib; and the tetraspores may be seen in pod-like leaflets attached to the bare midrib during the winter. Passing over some of the rarer membranaceous _Rhodymeniaceæ_, we come to the beautiful _Plocamium_, distinguished by its linear compressed crimson fronds, which are pinnate, with comb-like teeth, the branchlets being alternately arranged on either side in threes and fours. The spores are on radiating threads, in globular conceptacles; and the tetraspores are in the outer divisions of the frond. We have only one species of this beautiful genus, and that is _P. coccineum_, which is of such a brilliant colour that it is always a favourite with collectors. [Illustration: FIG 251..--_Plocamium_] Our last example of the order is _Cordylecladia_ (_Gracilaria_) _erecta_, with threadlike, cartilaginous frond, irregularly branched and cellular in structure. The fronds arise from a disc-like root; and bear spores in thickly-clustered spherical conceptacles, and tetraspores in lanceolate pods at the tips of the branches, both in the winter. It is a small weed, and grows principally on sand-covered rocks near low-water mark.