Phylogenetic analyses of liverworts using chloroplast rbcL and rps4 sequences were performed with special reference to the enigmatic thalloid liverwort, Mizutania riccardioides. The results showed that Mizutania is nested within leafy liverwort family Calypogeiaceae (subclass Jungermanniidae), thereby refuting the traditional interpretation that Mizutania is a member of the simple thalloid liverworts (subclass Metzgeriidae) related to Aneuraceae. Male plants with three ranked bracts, which are newly discovered in this study, also show a close morphological affinity to those of leafy liverworts. Parallel evolution of the flattened gametophyte seems to have occurred sporadically in the Jungermanniidae in association with adaptation to prostrate growth on the ground or on living leaves. The unistratose thalloid features of Mizutania are interpreted as an extremely reduced or highly specialized form of a creeping leafy liverwort. The rudimentary sexual branches which develop on the margins of the thallus are similar in many characteristics to those of Calypogeiaceae. We reduce the monotypic family Mizutaniaceae to a synonym of Calypogeiaceae.

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Two novel sugar acid-binding lectins were purified from Haplomitrium mnioides (Lindb.) Schust. using a procedure consisting of ammonium sulfate precipitation, G-50 gel filtration, hydroxyapatite chromatography, and HW-50 gel filtration. We reported their partial physicochemical properties: molecular weight, affinity for carbohydrates and organic acids, pH stability, and dependence of their hemagglutination activity on metal ions. We also determined their N-terminal amino acid sequences. H. mnioides lectins (HMLs) were monomers (one with a molecular weight of approximately 27 kDa, and the other with a molecular weight of approximately 105 kDa) under both nonreducing and reducing conditions. They were named HML27 and HML105, respectively. Both HMLs had an affinity for N-acetylneuraminic acid, D-glucuronic acid, D-glucaric acid, bovine submaxillary mucin, heparin, and organic acids, such as citrate, 2-oxoglutaric acid, and D-2-hydroxyglutarate. Furthermore, HML27 had an affinity for α-D-galacturonic acid, D-malate, L-malate, and pyruvate, while HML105 had an affinity for D-gluconic acid. HML27 and HML105 are novel plant lectins: they have an affinity for sugar acids and organic acids and specifically recognize the carboxyl group, and there is no homology between their N-terminal amino acid sequences and those of the previously described lectins and agglutinins.

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