^P. Olneyi^ (dough-balls). Fronds two to five inches high, densely tufted; soft filaments of hair-like fineness, much branched, and spreading; when in fruit covered with tiny balls or cystocarps; siphons four in number. It is common from Cape Cod to New York.
^P. fibrillosa.^ Frond four to ten inches high, rather robust below; main stem quickly lost in a number of prominent stems and spreading branches; irregularly and profusely branched, becoming ultimately very fine; numerous branchlets covered with colorless fibrils in hairy tufts, which give it a misty appearance; fibrils so delicate that they do not show well in dried specimens, but a distinct feature by which to recognize the species in the young plant; color light to dark brown; cystocarps adherent to branchlets or on short stalks; siphons four in number; main branches only corticated. It is common in summer on stones and on eel-grass, at low-water mark, from Cape Cod to New York. (Plate XXVII.)
^P. violacea.^ Fronds six to twenty-four inches high, pyramidal in general outline; main axis with long, wide-spreading branches at the base; branches rather robust and naked below, but numerous and becoming very fine and tufted at top; cystocarps adherent or on short stalks; siphons four in number; main stems corticated; ultimate branchlets show articulations; color brownish-red. It is common from New York northward. (Plate XXVII.)
^P. urceolata.^ Frond three to ten inches high; main stem bristle-like; branches naked below, divided and subdivided above; branches with short branchlets set at a wide angle and often recurved; siphons four in number; shows articulations; color deep red. Name refers to cystocarp, which resembles a pitcher. The plant grows in loose tufts, and is common from New York northward and on the California coast.
Variety ^formosa^. Filaments soft and finer than in /P. urceolata/; branches long and flexuous; articulations five to ten times longer than broad; color bright red. It grows in tufts sometimes a foot long, and is found only in the spring.
[Illustration: PLATE XXVII. Polysiphonia nigrescens. Polysiphonia fibrillosa. Polysiphonia violacea. Polysiphonia Woodii.]
[Illustration: PLATE XXVIII. Laurencia pinnatifida. Dasya elegans. Dasya plumosa. Dasya plumosa, magnified.]