. The Canadian field-naturalist. 180 The Canadian Field-Naturalist [Vol. ^). Fig. 3. Probable relationship of subsections and species of DRYAS. 1 and 3). All seem well adapted to unstable soils such as fresh moraines, gravel bars of glacial streams and erosion fans and, there- fore, do remarkably well in close proximity to glaciers. Pleistocene fossil remains of Dryas octo- petala have been found in peat bogs in many parts of Northern Europe. These remains have been dated back to the Riss and Wiirm glaciations when the species had a wider distribution than today (see also map in Hegi, , fi
. The Canadian field-naturalist. 180 The Canadian Field-Naturalist [Vol. ^). Fig. 3. Probable relationship of subsections and species of DRYAS. 1 and 3). All seem well adapted to unstable soils such as fresh moraines, gravel bars of glacial streams and erosion fans and, there- fore, do remarkably well in close proximity to glaciers. Pleistocene fossil remains of Dryas octo- petala have been found in peat bogs in many parts of Northern Europe. These remains have been dated back to the Riss and Wiirm glaciations when the species had a wider distribution than today (see also map in Hegi, , fig. 1175). In the Dryadeae the genus Dryas certainly seems most closely related to Sieversia and to the purely North American genera Fallu- gia and Cowania. It seems hazardous, how- ever, without genetical and palaeontological evidence, to attempt to draw any conclusions regarding the possible place of origin of the genus. A comparison of fig. 1 which gives the v/orld distribution of the genus, with fig. 2 showing maximum glaciation in the northern hemisphere, shows that the genus has reached its highest development in the largely unglaciated Eastern Asia and Northwestern America. In fig. 3 I have attempted to show the probable relationship of sub-sections and species of Dryas. PART II. TAXONOMY DRYAS L. Sp. PI. 501, 1753. Low, depressed, strongly caespitose under- shrubs with long, weak tap-roots and much branched, freely rooting, often metre-long and 1 cm. thick, dorsiventral, radial branches. Under favourable conditions forming circular patches that, in Dr. Drum- mondii, may attain a diameter of several metres. Leaves alternate, leathery, tardily decidu- ous, petioled, simple, crenate or entire, dark. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Natur
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