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The genus Bostrychia Montagne s.l. is reassessed. Two genera are recognised. Bostrychia and Stictosiphonia J.D. Hooker et Harvey, differing from eachother by the number of tiers of pericentral cells per axial cell, the mode of cortication and the number of indeterminate axes. These genera are described and keys are provided to all species. Bostrychia consists of 11 species. One of which, B. tenussima R.J. King et Puttock, sp. nov., is newly described from New Zealand and temperate Australia. Detailed descriptions are given for the other six species, B. harveyi, B. moritziana, B. pinnata, B. radicans, B. simpliciuscula and B. tenella, that occur in the Australasian region. Taxonomic notes are provided for the type of species. B. scorpiodes, which is restricted to western Europe, and three lesser known species, B. callipters, B. montahnei and B. pilulifers, from the Central and South American regions. Stictosiphonia is resurrected and emended. This genus consists of six species, two of which have tropical distributions, S. kelanensis (Grunow ex Post) R.J. King et Puttock, comb. nov. (southern and eastern Asia and northern Australia) and S. tangatensis (Post) R.J. King et Puttock, comb. nov. (eastern Africa and northern Australia). The remaining four species, S. hookeri, S. vaga, S. arbuscula (J. D. Hooker et Harvey) R.J. King et Puttock, comb. nov. and S. gracilis R.J. King et Puttock, sp. nov., have a southern Australian, New Zealand or subAntarctic distribution.

The genus Caloglossa J. Agardh is revised and eight species are recognised. One new species is described (C. adhaerens R. J. King et Puttock, sp. nov.), one new combination is made (C. bengalensis (G. Martens) R. J. King et Puttock, comb. nov.), and two forms of C. leprieurii are raised to specific status (C. triclada (E. Post) R. J. King et Puttock, stat. nov. and C. continua (Okamura) R. J. King et Puttock, stat. nov.) In Caloglossa continua four subspecies are recognised: C. continua ssp. continua; C. continua ssp. avillaris R. J. King et Puttock, ssp. nov.; C. continua ssp. postiae R. J. King et Puttock, ssp. nov.; and C. continua ssp. saigonensis (Tanaka et Pham-Hoang HB) R. J. King et Puttock, stat. nov. Detailed descriptions, taxonomic notes and a key are provided for these taxa and the previously described species that we recognise in the genus (C. beccarii (Zanardini) De Toni, C. leprieurii (Montagne) J. Agardh, C. ogasawaraensis Okamura and C. stipitata E. Post). Caloglossa leprieurii var. angusta Jao is a synonym of C. continua ssp. saigonensis, and C. adnata f. divaricata E. Post is included within C. leprieurii.

The effects of organic osmolytes synthesised and accumulated by red algae from mangrove habitats were investigated on the in vitro activities of two major enzymes, one of the citric acid cycle (malate dehydrogenase, MDH) and one of the oxidative pentose phosphate pathway (glucose-6- phosphate dehydrogenase, G6PDH). These enzymes were extracted from the mangrove algae Bostrychia tenella, Caloglossa leprieurii, Catenella nipae and Stictosiphonia hookeri. In each case, activity of the enzymes was inhibited with increasing NaCl concentrations up to 600 mM . In contrast, equimolar concentrations of mannitol (the major osmolyte in C. leprieurii), sorbitol (the major osmolyte in B. Tenella and S. hookeri) and a heteroside mixture (of which floridoside is the major osmolyte in C. nipae) did not inhibit enzyme function. Dulcitol, the second most important organic osmolyte in B. tenella, exerted no negative effect at its maximum solubility of 180 rnM on the salt-sensitive MDH. These data are all consistent with the proposed function of these organic compounds as compatible solutes.

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