A revision of the seven species of Rhododendron sections Sciadorhodion, Viscidula and Rhodora (of subgenus Pentanthera; Ericaceae) is presented. A cladistic analysis of Rhododendron subgenus Pentanthera is provided, and results in the recognition of four sections: Sciadorhodion, Viscidula, Rhodora and Pentanthera. The species are delimited and compared, their distributions are mapped, and descriptions and practical keys are developed.

The ‘Hebridean Marsh-orchid’ is a controversial dactylorchid taxon currently regarded as endemic to the island of North Uist in the Scottish Hebrides. Re-evaluation of past taxonomic treatments reveals that none of its three names – Dactylorhiza majalis (Reichenbach f.) P. F. Hunt & Summerhayes subsp. scotica Nelson (1976, 1979), D. majalis subsp. occidentalis (Pugsley) Soó var. ebudensis Wiefelspütz (in Landwehr, 1977), and D. majalis subsp. occidentalis var. scotica (Nelson) R. M. Bateman & Denholm (1983) – has been validly published. We herein legitimize D. majalis subsp. occidentalis var. ebudensis Wiefelspütz ex R. M. Bateman & Denholm, presenting for the first time full details of its lectotype. However, we also note that this nomenclatural clarification has no relevance to determining the most appropriate rank for, and biological significance of, this taxon, which is one of many doubtfully distinct ‘critical’ taxa of dactylorchids that occur in western and northern regions of the British Isles. Taxonomic opinions expressed on these populations to date have been based on sparse, qualitative, and often contradictory data, and most lacked an explicit conceptual framework. We outline a more rigorous analytical protocol.

A new monotypic genus, Distichochlamys (Zingiberaceae; Hedychieae), and its species, D. citrea, are described from central Vietnam. Its affinities lie with Scaphochlamys and Boesenbergia and, through them, to the wider group containing Kaempferia and Haplochorema.

A heterogenic system of incompatibility is described in Coprinus bisporus which involves two alleles at two loci, in addition to the unifactorial homogenic incompatibility locus already described for this two-spored species. The patterns of non-allelic heterogenic incompatibility found in C. bisporus are used to predict those expected in species with bifactorial homogenic incompatibility. This type of heterogenic incompatibility could lead to speciation.