Chorda Stackhouse 1797

Chorda is a genus of thalloid brown algae including two species. It is the only genus in the family Chordaceae. Its members are known by a number of common names including: mermaid's fishing line, tsurumo, ruálach, doruithe briain, sea laces, mermaids line, roccálach, ruadhálach, gemeine meersaite, bootlace weed, seatwine, zottige meersaite, dead men's ropes, mermaid's tresses, cat gut and sea lace.

Annual, growing on small shells or epilithic, subtidal. Sporophyte gregarious on small discoid holdfast, up to several meters in length, olive to brown, cord-shaped, cylindrical, solid when young later becoming hollow, composed of 3-8 cell rows of medullary layer, 4-6 celled paraphyses and narrow obovate unilocular sporangia. Trumpet-shaped hyphae present in the central part of thalli. Phaeophycean hairs (C. filum) or assimilatory hairs (C. tomentosa) abundant. No special mucilagenous organs. Chloroplasts many, discoid, without pyrenoids. Intercalary meristem present or absent. Plurilocular sporangia not formed on erect thalli. Life history heteromorphic between macroscopic polystichous sporophyte and branched filamentous gametophyte. Gametophytes oogamous, dioecious but sexually monomorphic (C. filum) or monoecious (C. tomentosa). Zoospores from unilocular sporangia teardrop-shaped, biflagellated with longer anterior flagellum, with a stigma. Germination unipolar forming emptied embryospore. Antheridia formed on fertile branches, often in cluster. Sperm almost colorless containing several reduced chloroplasts without stigma, with longer posterior flagella. Oogonia terminal on fertile branches. Zygotes develop attached at the mouth of the oogonia. First several divisions occur transversely, then become polystichous and terete. Sexual pheromone reported to be multifidene in C. tomentosa.