[Illustration: PLATE XXX. Chondria dasyphylla. Callithamnion americanum. Callithamnion Pylaisæi. Callithamnion Pylaisæi, a piece magnified.] ^C. americanum.^ Frond three to six inches long, densely tufted; filaments of extreme fineness; main branches alternate; much branched; main and secondary branches have pairs of branched ramuli along the [pg091] branches; color rose-pink. It grows on wharves and on algæ below low-water mark, and is a common and beautiful species. It is found (but only in the spring) from New York northward, and is abundant in Long Island Sound. (Plates XXX, XXXI.) ^C. Pylaisœi.^ Fronds three to six inches long, more robust and darker in color than in /C. Americanum/; main and secondary branches alternate, decompound, all bearing at short intervals short opposite branchlets, which in turn are covered with ramuli. It is found in spring on wharves and on algæ from Boston northward. (Plate XXX.) ^C. Baileyi.^ Fronds one inch to three inches long, with main stem as thick as a bristle, and running to the top of the frond; branches around the main stem longer at the base than at the apex, giving the plant a pyramidal outline; branches also have a main stem and short branches beset with branchlets; shrub-like in aspect; color purplish-red. Common in summer from New York to Cape Cod. ^C. seirospermum.^ Frond two to five inches high, pyramidal in outline; has main stem and alternate lateral branches; branches have secondary branches beset with delicate, erect branchlets; hair-like in fineness. It is common from Cape Cod southward, and is plentiful in Long Island Sound. (Plate XXXI.) ^C. byssoideum.^ Fronds one inch to three inches long; filaments very delicate; main branches many times divided; secondary branches long; many branchlets; rose-colored. It grows in globose tufts, and is common in Long Island Sound. (Plate XXXI.) ^C. floccosum.^ Fronds three to six inches long, hair-like in fineness; flaccid; main branches sparingly branched below; numerous alternate branches above; all clothed with short, simple branchlets; color dark brownish-red. The plant is so exceedingly fine that it is difficult to distinguish the divisions. It grows on eel-grass and on algæ below low-water mark, and is found from New York to Cape Cod. (Plate XXXI.) GENUS ^Griffithsia^ (/Named for Mrs. Griffiths, an English algologist/) These are among the most beautiful of seaweeds, because of their brilliant color and exceedingly delicate structure. They grow in deep water, and specimens cast ashore are usually torn and imperfect, but they may often be gathered from deep tide-pools, and sometimes are found growing on eel-grass. If placed in fresh water they discharge their coloring-matter and quickly decompose.