The species of this subclass are very numerous, and the variety in their fronds, their delicate texture, and their colors, which vary from pink to purple, make them the most attractive of the seaweeds. They grow mostly in deep water, but are often found washed ashore, and many grow just below low-water mark and on the shady side of tide-pools. In the simplest species the frond consists of branched cell-rows. In some of these the filaments are so fine that a pocket-lens is required to determine the differences in branching and fully to appreciate the beauty of the plant (/Callithamnion/). Some have a cell-surface. In /Delesseria/ the membrane assumes the outline of a foliage-leaf. /Dasya/, which is an abundant variety, is especially beautiful in its feather-like appearance. The corallines are singular in that they are incrusted with lime and resemble corals. ORDER =NEMALIONACEÆ= SUBORDER ~HELMINTHOCLADIEÆ~ GENUS ^Nemalion^ The threadweeds. ^N. multifidum.^ Frond six to twelve inches long, cylindrical, solid, cord-like, elastic, tough, shiny, very gelatinous; branches repeatedly in [pg080] a wide-forking manner; sometimes a branch will divide into several parts at the same point; color dark brown or purple. It is found, in summer only, from Long Island Sound northward, growing on smooth rocks which are exposed to the action of the waves. GENUS ^Liagora^ Fronds filamentous; branching regularly in a forking manner to the very top, forming thick bunches; slightly incrusted with lime, yet somewhat viscid. It is found in Florida and California, and abounds in tropical waters. SUBORDER ~CHÆTANGIEÆ~ GENUS ^Scinaia^ ^S. furcellata.^ Frond cylindrical, one eighth of an inch in diameter, tapering at base, sometimes constricted at intervals, regularly and several times forked, ending in short divisions; branches of same length, giving a level top; two to four inches high; lake-red. When pressed the axis is visible, giving the appearance of a flat frond with a midrib. This species is found in summer only, washed ashore from Cape Cod southward and on the California coast. It is not common. (Plate XVII.) SUBORDER ~GELIDIEÆ~ GENUS ^Gelidium^ ^G. corneum.^ Frond flat and horny, one inch to four inches high, narrow, erect, branched several times in the same plane; ultimate branchlets club-shaped, or swollen at the tips with masses of spores; color purple-red. It grows in tufts on mud-covered rocks, and on algæ at low-water mark. The typical form is found in Florida and on the Pacific coast. Smaller plants are found all along the Atlantic shore. It is an extremely variable plant, and is often difficult to distinguish on this account. (Plate XVII.) [Illustration: PLATE XVII. Scinaia furcellata. Gelidium corneum. Gelidium Coulteri. Chondrus crispus.] ORDER =GIGARTINACEÆ= GENUS ^Chondrus^ Carrageen or Irish moss.