G. R. Wieland — Polar Climate in Time. 415 



with a belief in extensive lateral intermingling of African, 

 Notogsean and Neogsean life. Crossing and recrossing of 

 either of the polar areas we believe rarely to have taken place, 

 and certainly during periods of polar cold this becomes quite, 

 or wholly impossible. 



Now it follows from a priori reasons, that since vertebrate 

 stocks originated more and more frequently in the boreal area 

 as time went on, down to the Glacial epoch, there must have 

 been a preceding development of food plants of quite as 

 varied character as the animals themselves, and with one more 

 word we may turn to the plant record. Nothing could at the 

 present time be more satisfactory to paleontologists than the 

 discovery of polar localities yielding fossil vertebrates. As 

 justly remarked by Professor Nathorst in a letter to the writer, 

 " It is very curious that not a single mammalian bone has 

 hitherto been found in any Tertiary deposit within the Arctic 

 area." But this dearth of actual evidence is quite as much 

 due to the unfavorable conditions for the preservation of fossil 

 bones on the exposed surfaces in high latitudes as enumerated 

 by Nordenskjold and Palander, as to the lack of exploration. 

 One cannot but believe that in the course of time there must 

 be found in the high north evidence in abundance comple- 

 mentary to that of the Jurassic, Cretaceous and Tertiary verte- 

 brate-yielding horizons of America and Eurasia. 



The Argument for Polar Origins as Based on the Plants. 

 — In the case of the plants there is both a northern and conti- 

 nental record. Both taken together supplement and confirm 

 the evidence afforded by the vertebrates of the radiation of hardy 

 stocks from the polar area on a grand scale. Indeed it is on 

 the basis of the facts afforded by both the past and present 

 distribution of plants, that more or less well defended theories 

 as to the northern origin of the present temperate ffora, and, 

 a priori., fauna have from time to time been proposed. A 

 belief in a Scandinavian flora of great antiquity, occupying the 

 polar area and during the advent of the glacial period radiat- 

 ing out on every longitude and to every latitude, was held by 

 Forbes and Darwin fifty years ago. It was given a certain 

 basis in fact by Sir Joseph D. Hooker in his Outlines of the 

 Distribution of Arctic Plants in 1861, and later on Saporta in 

 the Revue de Deiix Mondes (1883), after the discovery of the 

 Cretaceous Arctic fossil florae, stated his belief in the Arctic 

 origin of the main groups of animals and plants far back in 

 geological time, and including man as well. The definite con- 

 ception, well fortified by facts, of a universal southward dis- 

 persion of plants from the northern polar area during Tertiary 

 time was, however, first conclusively formulated and pre- 

 sented by Asa Gray in his Dubuque Presidential Address before 



