In a population of Pogonatum neesii (C. Mull.) Dozy at Kochi City, seasonal development was investigated for archegonia and sporophytes, together with the development of calyptrae and vaginulae. Archegonial production begins in mid-April with quick development and maturation in early to mid-May. Meiosis is observed in mid- to late September. The operculum with a calyptra falls in early March. Soon after fertilization, cells of archegonial stalk divide vigorously to form an envelope (embryotheca or embryonic calyptra) enclosing the embryo. The growing embryo passes down the venter into the tissue during development the of embryotheca. The fully developed embryotheca divide horizontally into a calyptra above and a vaginula below. the calyptra therefore originates from the archegonium stalk, not from the venter wall of the archegonium as known in many other mosses. On fertilization, hairs arise from the epidermis of archegonium stalk. These hairs covering a calyptra are oriented upward and derived mostly from the basal part of archegonium stalk.

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Ajisu Reclaimed Land (286ha) on the coast of the Inland Sea of Japan in Yamaguchi Pref. has been neglected for 23 years since its construction in 1965. To date, 344 species of vascular plants and 49 bryophytes including 44 mosses and 5 hepatics, have been found there, of which Helodium paludosum and Amblystegium humile, both species of the northern element growing on wet habitats, are noteworthy for their occurrence in SW Japan, where other known localities are limited for the former and absent for the latter.

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