1. Takakiaceae Murray
Authors: John R. Spence & W. B. Schofield
Stems erect, arising sympodially from creeping pale or white stolons bearing clusters of beaked slime cells, rhizoids lacking, stem in cross-section differentiated into an outer layer of smaller, thick-walled cells and a cortex of larger thin-walled cells, sometimes with small central cells, these often with trigones, outer cells with simple oil droplets. Leaves typically 3-ranked, terete, forked, of (1--)2--4 terete segments, segments sometimes connate at base, in cross-section of 3--5 cells, one or more larger central cells surrounded by smaller cells, oil droplets present in all cells, 2-celled slime hairs with enlarged apical cell present in axils of leaves. Specialized asexual reproduction by caducous leaves or stems. Sexual condition dioicous, gametangia naked. Seta with foot, persistent, elongating prior to capsule maturation. Capsule erect, symmetric, lacking well-defined neck region, lacking stomates, dextrorsely spiralled at maturity, columella ephemeral, basifixed, not penetrating the archesporial tissue, peristome lacking, dehiscence by a longitudinal helical slit. Calyptra fugacious to rarely persistent, typically mitrate. Spores 3-radiate, slightly roughened to papillose.
Genera 1 (1 in the flora): North America, se Asia (including Borneo); cool, cold-temperate to Arctic-alpine oceanic climates.
Plants of this family were first collected in the Himalayas by J. D. Hooker and placed in the hepatic genus Lepidozia as L. ceratophylla by W. Mitten. For a long time, the consensus had been that it was a highly unusual liverwort with affinities to the Calobryales. Distinctive features include the erect shoots arising from a stolon , terete leaves, sometimes fused at or near the base and thus of 2--4 segments, naked lateral gametangia, slime cells, oil droplets, and chromosome numbers of n = 4 or 5. In 1993, sporophytes and antheridia were discovered in a population from Atka Island of the Aleutian Islands (D. K. Smith and P. G. Davison 1993). The sporophyte exhibits its affinity with the mosses, and is similar in some respects to sporophytes of the Andreaeopsida, by the columella, persistent seta, capsule that matures after seta elongation, dehiscence by a diagonal slit, and lack of elaters. R. M. Schuster (1997) suggested that gametophytically Takakia is more like a liverwort, and sporophytically more like a moss. The Japanese common name is perhaps most telling, literally translated as “puzzling moss."
SELECTED REFERENCES
Hattori, S. 1963. Takakia of North Borneo (1). J. Jap. Bot. 38: 215--217. Hattori, S. and H. Inoue. 1958. Preliminary report on Takakia lepidozioides, J. Hattori Bot. Lab. 19: 133--137. Hattori, S., A. J. Sharp, M. Mizutani and Z. Iwatsuki. 1968. Takakia ceratophylla and T. lepidozioides of Pacific North America and a short history of the genus. Misc. Bryol. Lichenol. 4: 137--149. Hattori, S., Z. Iwatsuki, M. Mizutani and S. Inoue. 1974. Speciation of Takakia. J. Hattori Bot. Lab. 38: 115--121. Higuchi, M. and D. Zhang. 1998. Sporophytes of Takakia ceratophylla found in China. J. Hattori Bot. Lab. 84: 57--69. Renzaglia, K. S., K. D. McFarland and D. K. Smith. 1997. Anatomy and ultrastructure of the sporophyte of Takakia ceratophylla (Bryophyta). Amer. J. Bot. 84: 1337--1350. Schuster, R. M. 1997. On Takakia and the phylogenetic relationships of the Takakiales. Nova Hedwigia 64: 281--310. Smith, D. K. and P. G. Davison. 1993. Antheridia and sporophytes in Takakia ceratophylla (Mitt.) Grolle: evidence for reclassification among the mosses. J. Hattori Bot. Lab. 73: 263--271.
