Ellef Ringnes Island has a confirmed flora of 49 vascular plants and five parasitic fungi. The adjacent islands have less diversity of habitat and probably have even poorer floras. There are no endemics and the plants are extremely depauperate. The summer climate at Isachsen is colder than at any other station in the Canadian arctic. Although there are no convincing indications that Ellef Ringnes I. was overrun by a Wisconsin continental ice sheet, it cannot have escaped being snow-covered. The light cover of snow and ice on the outer islands was quickly lost in the postglacial xerothermic, which enabled plants to spread along the periphery of the archipelago. The numerous plants that occur south-west and northeast of these islands but not in them indicate that postglacial cold periods, probably accompanied by at least partial snow cover of the outermost islands, have driven out many species. Nearctic refugia are discussed and it is indicated, by analysis of distribution patterns, that no refugia occurred in the Canadian arctic archipelago. The region has been colonized from the Peary Land refuge, the Yukonndash;Alaska refugia, and from south of the retreating ice sheets.
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