^G. spinosa^ ("thorny"). Frond thick, leathery; surface rough and spiny; form variable, the divisions sometimes emanating from a broad, flattened base, or again branching from a main axis; all covered with the protruding processes peculiar to the genus; color dark red, brown, or purple. It is found on the California coast. (Plate XVIII.)
^G. microphylla^ ("small-leaved"). Plant rises from short, flat stem, and rapidly expands into a flat, wide, thin frond which is simple or divided into two or three segments, each of which tapers into a long, pointed apex; thickly covered with long, slender spines, and on its edges bearing small, thin leaflets; color brownish-red. It is abundant on the California coast. (Plate XVIII.)
Leafweed. Fronds cylindrical; branched stalks which expand into rigid, membranaceous, simple or cleft, wedge-shaped laminæ; laminæ bear leaflets on their edges or on their surface; spores in masses form projections on the surface, or are on stalks at the summit; color dark red. Found washed ashore from New York northward. [pg082]
^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.)