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Growth of the mycoheterotrophic gametophytes of Sceptridium dissectum and Ophioglossum crotalophoroides stalls at a few cells after germination on a nutrient medium lacking sugar. Resumption of growth when the cultures are supplied with glucose reveals that they are still alive. The stalled gametophytes of S. dissectum and O. crotalophoroides on media without sugar contain lipid droplets from the spores and a few starch grains that form during germination. The starch and lipid do not support the further growth of the stalled gametophytes because the size of the gametophytes does not change over time. These storage products slowly disappear from the stalled gametophytes. It appears that the storage materials are used to keep the stalled gametophytes alive. About 9% of the stalled gametophytes of O. crotalophoroides remain alive for ten months and about 5% of those of S. dissectum remain alive for 34 months. Delayed gametophyte growth is also exhibited by young gametophytes of Botrypus virginianus, Lycopodium obscurum, and Psilotum nudum. Delayed growth of mycoheterotrophic gametophytes under natural conditions would increase the time available for colonization by appropriate mycorrhizal fungi.
The systematic position of the fern genus Mesopteris is described and discussed based on its sole species, M. tonkinensis. Evidence for its generic separation is based on its gross morphological characteristics, leaf epidermis, gametophyte development, spore morphology, and chromosome numbers. A morphological comparison with other related genera of Amphineuron, Cyclosorus, Dryopteris, Lastrea, and Thelypteris is provided.
A new subgenus of Lastreopsis, subg. Rhopalotricha, is here described based on the results of our recent phylogenetic analyses. Its species differ from others in the genus by having a distinctive type of hair within the grooves of the rachises and costae adaxially. These are 1–3(–4)-celled and clavate, whereas the remainders of the species in the genus have hairs that are 3–12-celled and non-clavate. Subgenus Rhopalotricha also differs by having spores with broadly folded perispores with echinulate surfaces (vs. tuberculate or spiny, and with smooth surfaces). Subgenus Rhopalotricha occurs in the Neotropics, islands of the southwestern Pacific (Samoa, Fiji, and Vanuatu), New Zealand, and Australia. A key is provided to distinguish the species, each of which is treated with synonymy, description, geographic distribution by country, elevation ranges, and discussions. Lectotypes are also designated for Dryopteris amplissima var. subeffusa, Aspidium macrum Fée, and Aspidium latissimum Fée.
Aglaomorpha cornucopia (Copel.) M.C. Roos is an endemic and rare epiphytic fern from the Philippines. Ex situ germplasm storage and growth are important complementary tools for conserving this rare fern. This study was conducted to document the reproductive biology of this species. Mature sporophylls of A. cornucopia were collected in May, 2012 from Mt. Apo, the Philippines. Each sporangium bore 64 yellow, monolete spores. The average spore size was 49.3±3.7 µm. Fresh spores germinated 100% within one week of sowing (mean germination time (MGT) <1 week). Air-dried mature spores remained completely viable even after one year of storage at 3°C, although mean germination time was somewhat delayed (MGT = 1.4 weeks). Spore germination was of the Vittaria-type, whereas gametophyte development was of the Drynaria-type. Adult gametophytes were cordiform-annual and gametangia were of the leptosporangiate type. Unicellular papillate hairs appeared on marginal, dorsal, and ventral surfaces of the gametophytes. Gametophytes first produced antheridia and archegonia after seven weeks of culture. Gametophytes began to sexually produce sporophytes after 13 weeks of culture. The rate of sporophyte production reached 64% after 26 weeks culture. Results of this study suggest that cold temperature spore storage and in vitro culture offer reliable techniques for conserving this rare fern.
Hymenophyllum wrightii is a filmy fern known primarily from Japan and Korea. In North America, it is known as a sporophyte only in Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada. Rare independent, filmy fern gametophytes found from the late 1950s and onward at a handful of locations in British Columbia and southeastern Alaska were presumed to be H. wrightii. Our 2006 surveys in southeastern Alaska determined that these gametophytes are common within specific habitats, and our survey in 2008 found gametophyte populations on the Olympic Peninsula in Washington State—the first report of H. wrightii in the contiguous United States. Samples from gametophyte populations from southeastern Alaska, British Columbia and Washington show no variation in rbcL or rps4-trnS sequence and are similar to sequences from Asian H. wrightii sporophytes, providing corroborating evidence of the identity of these independent gametophyte populations.