On the life history of Pseudochorda nagaii (Pseudochordaceae fam. nov.) and its transfer from the Chordariales to the Laminariales (Phaeophyta)

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Abstract
The phenology and life history in culture of Pseudochorda nagaii, previously placed in the Chordariales, were studied. At Hanasaki, Hokkaido, Japan, the species is an annual, appearing in June, maturing in November-December, and disappearing the following July-August. In culture this species alternates between a microscopic filamentous oogamous gametophyte and a macroscopic parenchymatous sporophyte. The presence of oogamous reproduction and the parenchymatous construction of the sporophyte provide evidence that the species belongs to the Laminariales and not the Chordariales. However, P. nagaii differs from other Laminariales as follows: in the early developmental stage the apical segment of the sporophyte is asymmetric and lacks a phaeophycean hair; the paraphyses of the sporophyte are multicellular; and the gametophyte is monoecious and produces distinctive plurilocular antheridia. Consequently, the Pseudochordaceae fam. nov. is proposed to accommodate Pseudochorda within the Laminariales. Sporophytes develop and mature at temperatures of 10.degree. C or less. Gametophytes mature in 5.degree. C short-day conditions, which corresponds to winter in Hokkaido.

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