Bilberry and Heather 247 
Similar in the story they have to tell are the 
Scottish Menziesia (Phyllodoce ceerulea) and the 
Trailing Azalea (Lowselewria procumbens), the first 
found in this country only rarely on the Sow of 
Atholl in Perthshire; and elsewhere, in the Arctic 
portions of Europe, the mountains of Western France, 
the Pyrenees, Northern Asia, and North America. 
Trailing Azalea is also an alpine plant, whose British 
range extends only from Ben Lomond to Shetland, 
at altitudes between 1500 and 3600 feet. Elsewhere 
this plant occurs only in Arctic and Alpine Europe, 
Asia, and America; so that these two plants are 
representatives of quite other climatal conditions 
than those which induced the Heaths to penetrate 
northwards — they are remnants of a _ vegetable 
invasion from Northern Scandinavia during the 
Glacial Period, when the cold was sufficiently intense 
to allow such plants to extend over the old land 
surfaces as far south as the Pyrenees. 
