"Outlines of the Distribution of Arctic Plants," J.D.Hooker, "Trans.

Linn.

Soc." Volume XXIII., page 251, 1862.
[read June 21st, 1860.] In this paper Hooker draws attention to the exceptional character of the Greenland flora; but as regards the paucity of its species and in its much greater resemblance to the floras of Arctic Europe than to those of Arctic America, he considers it difficult to account for these facts, "unless we admit Mr.Darwin's hypotheses" (see "Origin," Edition VI., 1872, Chapter XII., page 330) of a southern migration due to the cold of the glacial period and the subsequent return of the northern types during the succeeding warmer period.

Many of the Greenland species, being confined to the peninsula, "would, as it were, be driven into the sea--that is exterminated" (Hooker, op.

cit., pages 253-4).); but there must have been at all times an Arctic region.
I found the speculation got too complex, as it seemed to me, to be worth following out.
I have been doing some more interesting work with orchids.