- Blue markers: specimen records
- Yellow marker: type locality, if present
- Red markers: endpoints of range from literature
Helminthocladia J. Agardh 1851
Thalli little to much branched, but only to 3 or 4 orders of branches. Medulla forming a core of slender, tightly woven longitudinal filaments. Cortex of dichotomously divided filaments, the outermost of these obovate to clavate in shape, this characteristic of genus. Chloroplast 1 per cell, parietal or irregularly lobed, with or without pyrenoid. Tetrasporangia rare, in some species occurring in position normally occupied by carposporangia. Spermatangia in terminal tufts, some occurring in short panicles. Carpogonial branch of 3 or 4 cells, lateral on low or medianly placed vegetative filament. Zygote after fertilization dividing obliquely (occasionally appearing to divide longitudinally) and forming relatively small gonimoblast, this with terminal carposporangia. Sterile filaments varying from few to many.
Helminthocladia australis Harv.
Harvey 1863: 39; Womersley 1965: 470. Helminthocladia australis f. californica J. Agardh 1899: 96. H. californica (J. Ag.) Kylin 1941: 6; Abbott 1965: 95. H. gracilis Gardner 1926: 206.
Thalli pyramidal, 15-20(36) cm tall, with cylindrical branches 2-4(6) mm diam., the branching of 3 or 4 orders, the density of branching varying with specimens and possibly related to habitat; older thalli sometimes hollow owing to loss of medullary filaments, otherwise the medulla consisting of slender, tightly woven filaments, these very tough and slippery; cortical filaments 4 or 5 times dichotomously branched, the terminal branches frequently clustered irregularly; terminal cells of filaments in Calif. material obovate, 50 µm diam. at top, tapering to 10(12) µm; spermatangia in short, paniculate clusters; carpogonial branch of 3 cells, the carpogonium dividing longitudinally after fertilization; small gonimoblast formed with terminal carposporangia; basal and adjacent cells of carpogonial branch frequently fusing; sterile filaments varying in number, in Calif. material not conspicuous because of resemblance to surrounding vegetative filaments.
Infrequent, saxicolous, low intertidal, Santa Barbara, Calif, to Pta. Pequena, Baja Calif., into Gulf of Calif. Also known from S. Africa, Japan, New Zealand, and Australia. Type locality: W. Australia.
Excerpt from Abbott, I. A., & Hollenberg, G. J. (1976). Marine algae of California. Stanford University Press, Stanford, California. xii [xiii] + 827 pp., 701 figs.
