122 B Canadian Arctic Expedition, 1913-18 



originated from more than one centre, yet given rise to species so closely related 

 as the two in question: P. caeruleum and P. boreale. The question as to their 

 original centre seems just as complicated as that of Sieversia. 



A similar difficulty arises when we consider Phlox Richardsonii, a 

 member of a genus so exceedingly well exemplified in the Rocky mountains, and 

 yet this species is known, so far, only from a very few stations on the arctic 

 American coast. No other explanation seems plausible than the considering of 

 the species as a remnant of the glacial flora, and as the sole remnant of the 

 genus, formerly distributed much farther north but exterminated with but this 

 exception at the high-northern latitudes. 



Very few Boraginaceae have been found in the arctic region. Ledebour, 

 for instance, mentions only 1 species of Mertensia, 4 species of Myosotis, 1 species 

 of Eritrichium, and 2 species of Echinospermum as. occurring in arctic Russia, 

 and only 1 species of Myosotis, and 1 oi Eritrichium as inhabiting arctic Siberia; 

 no additional species are recorded by Kjellman from the north coast of Siberia. 



Of these Myosotis silvatica was found on the north coast, but only the typical 

 plant; in the arctic region the variety alpestris Koch is more common and, as 

 described by Ledebour as being "humilior, racemis brevioribus densius incum- 

 benti-pilosis, pedicellis crassioribus, calycibus majoribus," it is quite distinct 

 from the type. According to Ledebour the typical plant has been found in 

 arctic Russia but nowhere in Siberia, except in the Altai mountains and Davuria. 



While Mertensia paniculata has been reported from many stations in 

 Canada and the United States, M. Drummondii has never been found outside 

 the north coast where, moreover, it seems to be extremely rare. These two 

 species belong to the section Eumertensia which is quite well represented in 

 the Rocky mountains especially, and the occurrence of M. Drummondii solely 

 on the north coast may be explained in the same manner as that of Phlox Rich- 

 ardsonii. But with respect to M. maritima, this is a seashore plant and, although 

 wholly absent from the Siberian coast, it is not infrequent on the arctic coast of 

 this continent, as well as in Greenland and arctic Europe. Being a seashore plant, 

 and at present so widely distributed in Europe and on this continent, the species 

 evidently belongs to the category of plants which originated in the south but 

 gained a more extended distribution toward north when the ice receded, like 

 Halianthus. 



The large family of Scrophulariaceae is in the arctic region well exemplified 

 by the genus Pedicularis but the other genera are very poorly represented; 

 for instance, according to Ledebotir: Limosella, Veronica, Castilleja, Bartsia, 

 Euphrasia, Rhinanthus, and Melampyrum are the only ones, besides Pedicularis, 

 known from arctic Russia; Veronica, Castilleja, and Pedicularis are the only genera 

 known from arctic Siberia. But among these arctic Eurasian genera is one which 

 more properly belongs to the North American flora, viz.: Castilleja. Of this 

 genus C. pallida and the variety septentrionalis Gray, so widely distributed in 

 Canada and in the mountains of the United States, viz. : the alpine summits of the 

 White mountains and Green mountains of New England, and throughout the 

 Rocky mountains, occur, furthermore, in arctic Russia and Siberia, in Ural, 

 Altai and Baikal, in Davuria and in Kamtchatka, besides in Alaska, and in 

 South Greenland. The geographical centre seems naturally located in the 

 Rocky mountains where the species is associated with several closely related 

 congeners and from where it became distributed to the north, extending east- 

 ward to the American archipelago and Greenland, westward across Bering 

 strait to Siberia and arctic Russia. 



With respect to Pedicularis, the accompanying table (Table 8) shows the 

 species which have been recorded from the polar regions. This table comprises 

 only 16 species, a small number, indeed, when we bear in mind not only that 120 

 species are recognized as "valid species" by Bentham and Hooker but also, and 

 quite especially, that the arctic element represents sections so exceedingly well 



