^G. Bornetiana.^ Fronds two to five inches high; filaments jointed, the divisions being long and pear-shaped, growing shorter as they near the top; repeatedly forked; very soft and fragile. It grows in tufts, resembling corals; attains perfection in July, and disappears later in the summer. Found from Cape Cod southward, washed ashore after storms. (Plate XXXII.) [pg092] GENUS ^Ptilota^ Feather-weed. ^P. serrata.^ Fronds three to six inches long, dark red in color, cartilaginous; flattened main stem with opposite, flattened branches, one of which is minute, so that it appears like alternate branching; branches also have lateral branchlets and pinnulæ, looking like feathers or ferns; all branching in one plane, making a flat frond. It is found in the drift on the beach after a storm, and is common from Cape Cod northward, and also on the California coast. (Plate XXXII.) ^P. elegans.^ Narrower and more delicate than /P. serrata/, otherwise it has the same essential features. It is common in summer from New York northward, growing on cliffs, under /Fucus/, near low-water mark, and it is also found washed upon the beach. (Plate XXXII.) ^P. densa.^ Frond three to twelve inches high, one eighth of an inch wide, flat, cartilaginous; has leading stem with flat alternate branches; branches simple or branched again; edges of whole plant beset with notched, curved pinnulæ alternating with smaller feather-like pinnulæ, giving a dense edge to all parts of the frond. It is found on the California coast. (Plate XXXIII.) ^P. hypnoides.^ Flat, cartilaginous main stem, much branched, and all beset with pinnulæ. It differs from /P. densa/ in having the alternate pinnulæ straight and club-shaped, instead of toothed and curved, and the plant is not so dense and compact. Found on the California coast. (Plate XXXIII.) GENUS ^Spyridia^ ^S. filamentosa.^ Fronds four to eight inches long; filaments as thick as bristles, irregularly and repeatedly branched; young branches show articulations and seem to be striped; all branches clothed with short, very delicate, transparent filaments, which give the plant a hazy appearance; color purplish-red, which becomes brown when dried; does not collapse when taken from the water. It grows in tufts below low-water mark, and is found in the drift on the beach from Cape Cod southward. (Plate XXXIII.) GENUS ^Ceramium^ The pitcher-weed. This genus is easily recognized by the ends of the filaments, which are forked and incurved, resembling minute pincers or claws. The filaments are also more or less distinctly banded. It is widely distributed. [Illustration: PLATE XXXI. Callithamnion americanum, a piece magnified. Callithamnion seirospermum. Callithamnion byssoideum, var. fastigiatum. Callithamnion floccosum.] [Illustration: PLATE XXXII. Griffithsia Bornetiana. Ptilota serrata. Ptilota serrata, magnified. Ptilota elegans.]