Of the genus _Dumontia_ we have only one species (_D. filiformis_), the frond of which is a simple or branched tube, from an inch to more than a foot in length, containing a loose network of filaments when young, and only a gelatinous fluid when the plant is mature. The spores exist in rounded clusters among the cells of the tube, and the tetraspores are similarly situated. A variety with wide wavy fronds is sometimes found in the brackish water near the mouths of rivers. _Gloiosiphonia capillaris_ is a very delicate and beautiful weed found in the lowest tide pools of the south coast. Its frond is a very slender branched tube, filled with a gelatinous fluid, and composed of delicate filaments embedded in transparent gelatine. It is a beautiful object for the microscope. _Schizymenia_ (_Iridæa_) _edulis_ has flat, oval, dark-red fronds that grow in clusters; and, being eaten by various marine animals, is often found imperfect and full of holes. The fronds are sometimes a foot or more in length, and five or six inches wide. They are thick and leathery, and each is supported on a short, cylindrical stem. In the lower tide pools we commonly meet with _Furcellaria fastigiata_, with brownish-red, cylindrical fronds, solid, forked, and densely tufted. The branches are all of the same height, with sharp tips; and the spore-clusters are contained in terminal lanceolate pods. This weed is very much like _Polyides_, of another order, but may be distinguished by its fibrous, creeping root, while that of _Polyides_ is a disc. The genus _Chylocladia_ is characterised by a tubular rounded frond composed of two layers, the inner consisting of branching filaments, and the outer cellular. The spores are contained in external cones with a pore at the apex, and the tetraspores are among the superficial cells of the branches. There are two common British species of the genus, one of them--_C. articulata_--with long, tubular fronds, constricted at intervals, the lower branches forked and the upper whorled and tufted; and _C. clavellosa_, with freely branched fronds bearing short spindle-shaped branchlets. One of the best-known algæ of the present family is the Irish Moss or Carrageen (_Chondrus crispus_), which will be at once recognised by its representation on Plate VIII. Its fronds are cartilaginous, forked and fan-shaped; and, when growing in deep, sheltered pools, its branches are often broad and much curled. This weed is an important article of commerce, being still used as a food for invalids. When boiled it yields a colourless gelatine.