- Blue markers: specimen records
- Yellow marker: type locality, if present
- Red markers: endpoints of range from literature
Gelidium Lamouroux 1813
Thalli cartilaginous, to 30+ cm tall. Axes erect, terete to compressed, variously branched, sometimes strikingly distichous, red to deep purple or black. Plants saxicolous, attached to substratum by branched prostrate axes; proportions of prostrate and erect axes varying; plants sometimes occurring in mats of algal turf with extensive basal parts or in more discrete clumps with 1 or more axes arising from limited basal system. Cortex with several rows of pigmented cells, the smaller toward the outside, mostly 2-12 µm diam., irregularly arranged. Medullary cells in cross section generally rounded, 20-27 µm diam., colorless, compacted or loosely appressed, with or without evident starch granules. Rhizoidal filaments thick-walled, 2-5 µm diam., in medulla and/or cortex, varying in number and position within species and even within single plant. Tetrasporangia in sori at apices of branches, or extending over entire flattened lateral branchlet, or also extending into supporting branch beneath; tetrasporangial branchlets with or without distinct sterile margins; tetrasporangial plants often recognizable by dark, granular appearance of fertile branchlets, this resulting from size and intense pigmentation of spores. Spermatangial sori sometimes apparent as relatively unpigmented areas on apices of branchlets, usually conspicuous by presence of sterile darker margin. Carpogonial filament unicellular, fusing with adjacent cells after fertilization. Mature cystocarps protruding equally on both surfaces of branch, usually with single pore on each surface, rarely with 2 or 3; vegetative growth continuing apically beyond developing cystocarp, making its position more proximal.
The following are known only from the type collections from Calif., and their relationships cannot be ascertained; for the present they must be thought of as doubtful species: Gelidium contortum Loomis (1960), San Francisco; G. umbricolum Dawson & Neushul (1966), Anacapa I.; and G. venturianum Dawson (1958), Ventura Co.
Gelidium nudifrons Gardn.
Gardner 1927b: 274; Dawson 1953a: 65.
Plants to 35 cm tall, clumped, sparsely and irregularly branched; axes compressed to flattened throughout, with all parts of similar dimensions, 0.4-0.9 mm broad, 0.3-0.6 mm thick.
Occasional, on rocks, subtidal (to 30 m), S. Calif. and Channel Is. to Pta. Santa Rosalia, Baja Calif. Type locality: Ensenada, Baja Calif.
G. nudifrons and G. arborescens as diagnosed here do not overlap in geographic distribution; at present they are also separable by depth of subtidal occurrence and by the dimensions of branches. G. arborescens is more robust and stiff than G. nudifrons; but the latter, when grazed back to basal portions, can be deceptively like plants in the Pebble Beach population.
Excerpt from Abbott, I. A., & Hollenberg, G. J. (1976). Marine algae of California. Stanford University Press, Stanford, California. xii [xiii] + 827 pp., 701 figs.
