P. membranifolia. Several stems rise from same disk; branches expand into wedge-shaped, cleft or forked laminæ; lobes bear on the summit other laminæ or leaflets divided in the same manner.

P. Brodiæi. Stem less branched and leaf-expansions broader and larger than in P. membranifolia; laminæ wedge-shaped and deeply lobed. (Plate XIX.)

S. interrupta. Frond a thin membrane repeatedly forked, widely spreading, divisions one fourth to one half of an inch wide; fertile plants have the spores arranged in an interrupted line through the center of the segments resembling a midrib; frond two to eight inches high; bright red. It is found on the California coast. The illustration shows a plant on which the hydroid Sertularia pumila is growing. (Plate XIX.)

G. Norvegicus. Frond two to four inches high, thin but leathery in substance, flat, narrow, divided in a regular forking manner; spreading ends of terminal forks obtuse; axils rounded; spores form spherical masses in the upper segments, and project on both sides like hemispheres. It resembles a simple form of Chondrus crispus, but is more delicate. The color is red or purple. This species is found in deep tide-pools from New York northward. (Plate XIX.)

A. plicata. Frond coarse, stem-like filaments, stiff, wiry, irregularly and profusely branched; sometimes regularly forked and upper segments equal; entangled; six to eight inches long; tufts several inches in diameter; dark purple or black. Specimens long exposed on the beach are faded to white. It is very common from New York northward. (Plate XIX.)

C. variegata. Deeply cleft, wide-spreading, flat, membranaceous frond; all parts notched more or less angularly; color dark to bright red; spores form hemispherical warts on surface. Some varieties differ from this one in having long and narrow, and others in having short and broad segments. It is a beautiful and common alga on the Pacific coast, resembling Euthora of the eastern coast. (Plate XX.)

C. laciniata. Frond deeply cleft; segments wedge-shaped. It is found on the Pacific coast. (Plate XX.)

C. purpurascens. The translucent, fleshy, juicy main stem, one eighth of an inch or less in diameter, runs through the whole plant; irregularly branched all around main stem; branches again branch in same manner; branches attenuated at the base, and taper to a long point; smaller branches distended in places by spores into bladder-like swellings, hence the name; color rose-red to dark purple; plants exposed on the beach often faded to orange and white; six to eighteen inches long. It grows on rocks between tide-marks as well as in deep water. With the exception of Ceramium rubrum, this is the most common red alga on the eastern coast from New York northward. It differs from Rhabdonia in having bladdery branches; otherwise it is easily mistaken for it.

C. cirrhosa. Ends of branches terminate in spirals like tendrils; otherwise identical with C. purpurascens. (Plate XX.)

E. cristata. Frond one inch to five inches high, membranaceous, broadly spreading; divisions wide and numerous, ultimately becoming fine like minute branchlets, each one of which, under a glass, shows a notch in the tip. This beautiful, bright-red alga is found in abundance north of Cape Cod. It differs from Delesseria alata in having no midrib or veins. It grows in deep water on stones, shells, and algæ. (Plate XXI.)

R. veprecula. Frond two to five inches long, one fourth of an inch to one and one half inches broad, membranaceous, forked; margin covered with leaflets which are in turn edged with minute branchlets; color deep red. It is found on the northern New England coast. (Plate XXI.)

R. tenera. Frond six to eighteen inches long, cylindrical, fleshy, translucent, juicy; irregularly and profusely branched, branches longest at the base, erect, tapering at both ends, numerous branchlets; sometimes the main stem runs through the plant, sometimes it is lost in the [pg084] branching; spore-masses sometimes form knotty bunches on the side of branches. It resembles a large Cystoclonium purpurascens. It is characteristic of Long Island Sound, and is not found north of Cape Cod, but common from there southward along the whole Atlantic coast. (Plate XXI.)

R. Coulteri. This species is common on the Pacific coast, and differs from R. tenera in having a more pronounced leading stem, and branches shorter and crowded at the top of the frond.

E. isiforme. Frond grows in tufts a foot or more in diameter; stems branch in all directions from a central point, and taper gradually to the end; secondary branches spread to all sides; all branches swollen at intervals and armed with several spines spreading from a conical base; color dark red, becoming on exposure orange or yellow, and at length semi-transparent and horn-like; substance firmly cartilaginous. Abundant at Key West.

G. multipartita ("many times divided"). Frond four to twelve inches long; starting from a short, cylindrical stem, it flattens and broadens as it rises, dividing in an irregular, forking manner, or cleft into palmate segments which broaden as they rise, and which divide in the same manner; often cleft or branched on the edges; conical spore-masses scattered over the frond during July and August; dingy purple in color. The plant is variable and sometimes is difficult to determine. It is common from Cape Cod southward. A narrow variety is most abundant in Long Island Sound. In Florida and on the California coast there are broad varieties which may be mistaken for Rhodymenia. (Plate XXI.)

H. musciformis ("moss-like"). Frond six to twelve inches long; main stem running through, thick below and tapering to the size of a bristle; much and irregularly branched, especially at the base; branches wide-spreading in every direction, and longest at the base; branches branch again in the same manner; all parts beset with short, horizontal spines; color purplish-red. A characteristic feature, by which the plant can easily be distinguished, is that the ends of the long branches are naked and are turned over like a hook, or nearly twisted. It is found washed ashore, often in large, intricately twisted tufts, from Cape Cod southward and on the Pacific coast.

R. palmata ("hand-shaped"). The plant commonly known as dulse. Frond rises from a disk in a short cylindrical stem which spreads into a thin, broad, fan-shaped membrane six to twelve inches long and four to eight inches wide at the top; deeply and irregularly cleft into many wedge-shaped segments; margin usually entire, but often with leaflets; ends of segments indented, showing where divisions will ultimately occur; color dark purplish-red. It grows on rocks and on algæ below low-water mark, and is common on the New England and California coasts. This is an edible alga, and, like Chondrus crispus, is an article of food in seaports. (Plate XXII.)

L. Baileyana. Fronds two to five inches high; grows in tufts; filaments tubular, irregularly branched; branchlets often all on one side; branches and branchlets curved or arched, and tapered at both ends; color brownish-red. It is found washed ashore from Cape Cod southward. (Plate XXII.)

C. parvula. Frond two to six inches long, irregularly branched; grows in tufts; filaments hollow and constricted, so that they appear somewhat like a string of beads; color brownish-purple. It is found washed ashore from Cape Cod southward. (Plate XXIII.)

C. articulata. Frond filamentous, three to twelve inches long, hollow, constricted at intervals; branches emanate from constricted joints; has the appearance of a series of pink, delicate, oval sacs. (Plate XXII.)

P. coccineum ("scarlet"). Frond a flat, semi-cartilaginous main stem one eighth of an inch, or less, wide, three to eight inches long, with alternate branches of unequal length emanating from the edges; branches have alternate branchlets arranged in groups of three or four in a row; branchlets have pinnulæ on the upper side, like the teeth of a comb (this peculiarity in branching makes the genus easy to identify); color dark lake-red. It is not found on the eastern coast, but is plentiful in California. (Plate XXIII.)

N. laceratum. Frond expands from narrow base and divides almost at once into long, narrow, strap-shaped segments; minute leaflets, showing [pg086] a dot or spore-cluster, occur at intervals on the margin; plant six to eight inches long; thin and silky in texture. Abundant on the California coast. (Plate XXIII.)

N. Ruprechteanum. Frond one foot to two feet long, spreading from narrow base and dividing by forking into deep-cut, broad, strap-like lobes; top divisions rounded; traversed lengthwise by parallel veins; margin of the older parts bordered with a narrow frill of thin ruffled membrane which sometimes extends also over parts of the surface of the frond; substance somewhat rigid; color dark red to purple. It is found on the California coast. (Plate XXIV.)

N. punctatum. Frond six to twenty inches long and of the same width, dividing in a forking manner; crowded at top; when in fruit, covered with dark dots; substance thin and silky; color rose-pink. It is found on the California coast. (Plate XXIV.)

G. Americana. Frond a delicate membrane, rose-red or purplish in color, leaf-shaped, four to eight inches long, one inch to four inches wide, tapering at both ends; margin entire, but much waved; a line of darker color through the center resembles a midrib; masses of spores form dots or specks irregularly over the whole surface; grows from a disk and short slender stem in bunches on shells and stones in deep water. It is found washed ashore from Cape Cod southward, and is luxuriant in New York Bay, where it can be found at any season, but is in perfection in August. (Plate XXIV.)

D. sinuosa. Delicate, leaf-like membrane, with midrib and veins, much indented and resembling in general outline an oak-leaf; four to eight inches long, two to four inches broad; short stem; color dark red, often flecked with green. It grows in bunches in deep water, and is easily distinguished, since it is the only alga having a midrib and veins, and resembling the leaf of a tree. It is found washed ashore from Cape Cod northward. (Plate XXIV.)

D. alata ("winged"). Frond rises from short stem, which flattens and divides irregularly into many branches and appears like a midrib, all bordered with narrow membrane one eighth of an inch to one inch wide; frond two to four inches long; color light red or pink. It is found on the shore from Cape Cod northward. (Plate XXV.)

D. Leprieurii. Frond one inch to two inches long, very narrow, with delicate midrib, forked, constricted at intervals; branches start from constricted points; thin and delicate; color purple. It is found in tidal rivers near New York, and is common on the southern coast. (Plate XXV.)

P. fastigiata. This species grows on Ascophyllum nodosum in a globular tuft, and appears like a dark-brown ball, one inch to three inches in diameter. The frond is a dense mass of rigid filaments branching many times in a forking manner and at broad angles. The ends are of nearly equal length, giving the plant a spherical shape. It is common from New York northward at all seasons, and is easily recognized by its general form and place of growth. Egg-shaped cystocarps, or spore-cases, occur in the ends of the terminal filaments. (Plate XXV.)

P. nigrescens. Frond three to twelve inches long, rigid below, soft above; main stem thick as a bristle, but not always easy to distinguish; branches alternate and densely branched at the ends; siphons twelve to sixteen in number; filaments banded; color black or very dark brown. (Plate XXVII.)

P. parasitica. Frond one inch to three inches long; branched in a pinnate or feather-like manner; filaments flat; all branches and branchlets emanating from the edges and on the same plane, giving a flat frond; color reddish-brown; resembles a fine Ptilota plumosa; cystocarps on short stalks. It is found on the California coast. (Plate XXV.)

P. dendroidea. This is a variety of the species P. parasitica. Frond four to five inches long; main branches placed at irregular intervals, but the secondary branches at regular intervals and alternate; branches [pg088] set at acute angles, giving the plant a slender appearance; color black or dark brown. It is common on the California coast. (Plate XXVI.)

P. Baileyi. Frond three to six inches high, flat; branches emanate from edges of the flat stems; main branches wide-spreading and irregularly placed, secondary branches regular and alternate; branchlets one eighth to one half of an inch long, covered on the edges and around the top with incurved ramuli; branchlets broken off near the base of the branches in mature plants; branchlets usually uniform in length, but occasionally one is longer and branches like the primary stem; color black. Common on the California coast.

P. Harveyi. Frond two to six inches high; grows in globose tufts, and has a bushy aspect; branches stiff and wide-spreading; stems and branches beset with simple or branched spine-like branchlets; color dark brown, or black when dry; does not collapse when taken from the water; cystocarps on short stalks; siphons four in number. It grows on eel-grass and algæ, and is common in Long Island Sound and northward. Called locally niggerhair. (Plate XXVI.)

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.

P. variegata. Fronds four to ten inches high; filaments thick as a bristle below, and branched in a forking manner to the very top; divided at long intervals below, at the top becoming of hair-like fineness [pg089] and dividing rapidly, forming a densely tufted mass, which collapses when taken from the water; color purple-brown; when mounted, silky in appearance; filaments banded; siphons six in number. It forms purple tufts on woodwork and on eel-grass from Cape Cod southward.

P. Woodii. Fronds four to six inches high; branches flat, long, wide-spreading, emanating from the edges in one plane; younger branches show articulations; ultimate branchlets inclined to curve inward; color light brown. Found on the California coast. (Plate XXVII.)

L. pinnatifida. Frond flat, thick, leathery; main stem with opposite, or alternate, branches of about the same size and character as itself; all pinnatifid, or cut on the edges into branchlets, some of which are again divided; color bright purple, often unevenly faded. It is found on the Pacific coast. (Plate XXVIII.)

D. elegans. Fronds from six inches to three yards long; main stem and branches cylindrical, and all densely clothed with a fine, hair-like fringe, which gives the plant the appearance of chenille; cystocarps on stalks along the branches; color pink or lake-red. Out of water it seems like a mass of purple jelly. It is found at or just below low-water mark from Cape Cod southward, and is very plentiful in New York Bay. (Plate XXVIII.)

D. plumosa. A species found on the California coast. The fringe covering the stems consists of minute leaflets instead of hairs, as in D. elegans. (Plate XXVIII.)

B. rivularis. Fronds one inch high; color dark purple; branches fine and irregularly bent. It grows where the water is not very salt, and is found in patches on submerged logs near New York. Common from Charleston, South Carolina, southward. (Plate XXIX.)

R. subfusca. Frond six to eighteen inches long; main stem cylindrical, and branching widely on all sides; branches longest at base and gradually shortening to the top of the stem; branches naked below, but at the ends profusely branched, forming tufts of branchlets. It is a perennial plant, and changes in aspect with the season. When mature it is stiff and coarse, and when dry it is quite black. Common from New York northward.

R. Rochei. This species resembles in form R. subfusca, but is much finer and more delicate. In spring it is a soft, fine, feathery, and beautiful [pg090] alga of a red-brown color. It is found washed ashore, or in deep tide-pools, south of Cape Cod. (Plate XXIX.)

R. larix. Frond cylindrical, robust, six to fourteen inches high; branches of unequal length standing out horizontally all around the main stem; clusters of branchlets growing spirally around stem and branches. Found on the northern California coast. (Plate XXIX.)

R. floccosa. Frond four to ten inches high; less robust than R. larix; stem and branches flat and divided in one plane; branches alternate; ultimate branchlets somewhat incurved; color black. In fertile plants the terminal branchlets are gathered in a mass. Found on the California coast. (Plate XXIX.)

C. dasyphylla. Frond four to eight inches high; general outline pyramidal; branches alternate on main stem; stem and branches covered with short, club-shaped (blunt at top, attenuated at base) branchlets; cystocarps, or spore-cases, adherent to branchlets or on short stalks; color light or dull brown. It grows in tufts, and is common from New York to Cape Cod. (Plate XXX.)

C. tenuissima. This species is similar to C. dasyphylla, but is more slender, and the branchlets taper at both ends instead of being club-shaped.

C. striolata. A species similar to C. tenuissima. The branchlets bear secondary branchlets, and the cystocarps are on short stalks. It is plentiful in Long Island Sound.

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.)

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]

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.)

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.)

C. rubrum, red ceramium. This is a very common and robust species, found everywhere, and growing on everything. It is variable in appearance, becoming quite coarse when old, the incurving, claw-like ends, which are characteristic of the genus, being less pronounced. It branches by repeated forking, and, under the microscope, shows a bark-like [pg093] layer of cells over the whole surface, which make the ring-like bands on the filaments less conspicuous.

Variety proliferum. Fronds beset on all sides with simple or forked branchlets. (Plate XXXIV.)

Variety secundatum. Branchlets generally arranged on one side of the filaments, or secund.

C. strictum ("straight"). Brown or purplish-red filaments of hair-like fineness, growing in tufts two to six inches high, branching in narrow forks more and more closely as they reach the top of the frond. There are no principal branches, the filaments being of about the same diameter and regularly dividing in a forking manner throughout. The filaments are banded, the red rings being relatively very narrow. The white interstices at the base are several times longer than broad, but shorten gradually until at the top they are of equal length with the red bands. This species is common from Cape Cod to New York.

C. diaphanum. This species has comparatively stout leading branches, with secondary alternate branches which are finer than the main stems and divide in a forking manner throughout, and ultimately become very fine. The color is brown or purplish-red, distinctly banded. It grows on eel-grass and algæ, and is found from Cape Cod to New York. (Plate XXXIV.)

C. fastigiatum. Filaments of hair-like fineness and of about same size throughout; branched in regular forking manner throughout, the divisions being wide and distant at the base, but gradually becoming closer and narrower as they reach the top; the upper segments about equal, giving a level top and regular outline in mounted specimens; the terminal forks erect, or less incurved than in other species; small points or branchlets emanate from some of the nodes or joints between the bands of color; tufts globe-shaped, two to five inches high; color lake-red. This species grows on mud-flats and mud-covered rocks as well as on algæ and eel-grass.

C. tenuissimum. Fronds two to four inches high, densely tufted; the forked divisions very wide or open; color rose-pink.

Variety patentissimum. Fronds small; the forked divisions distant and very wide open. A mounted specimen appears somewhat like network. The species is common in Long Island Sound. (Plate XXXIV.)