| Summary: | The south-western limit area distribution of several arctic relict species (cranberries, Betula nana) occurs in the French Massif central. Although especially localised in a few relict bogs, Vaccinium sect. Oxycoccus show an unexpected cytological diversity with diploids (supposedly V. microcarpum) in several localities of the Massif central sometimes growing in mixture with tetraploids (putatively V. oxycoccos). For the first time in France, we identified hexaploid cranberries. These plants correspond to « Oxycoccos quadripetala (Gilib.) var. majuscula » Chassagne a large, highly floriferous pioneer taxa of lacustrian mires. Oxycoccus palustris var major Lange is also a large leaves cranberry but collected in the vicinity of Oslo. Respectively described from Auvergne in 1957 and from Scandinavia in 1883, these two plants have been ignored by all botanists and remained absent from botanical literature, which is why we typify them here. They could correspond to the same species. Then, a new ecological and evolutionary understanding of cranberries is possible. In any case, this underlines the extreme richness and originality of the Auvergne peatlands, which are now home for three species of cranberry among the four known in the world: V. microcarpum and V. oxycoccos (mostly ombrogenous peatland) and, the apoendemic V. majuscula (only in topogenous mire). Le Massif central français représente la limite sud-ouest de distribution de plusieurs espèces arctiques relictuelles (Betula nana). Bien que particulièrement localisés dans quelques tourbières, les Vaccinium sect. Oxycoccus y montrent une diversité cytologique inattendue avec des diploïdes (supposément V. microcarpum) dans plusieurs localités du Massif central qui poussent parfois en mélange avec des tétraploïdes (supposément V. oxycoccos). Pour la première fois en France, nous avons identifié des canneberges hexaploïdes. Elles correspondent à « Oxycoccos quadripetala (Gilib.) var. majuscula » Chassagne, un taxon très original (inflorescences portant 3-5 fleurs ...
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