420 G. B. Wieland — Polar Climate in Time. 



Eocene and probably Miocene plants, represented by nearly 

 three hundred species. The conifers, Taxodium, Thuja, Se- 

 quoia, Giugko, Abies and Pinus are present. Among the 

 Dicotyls are a profusion of oaks and walnuts, with j^oplars, 

 elms, ashes, planes, maples, chestnuts, alders, beeches, birches. 

 There are, moreover, bays, six species of magnolia, three of 

 ebony, and a soapberry, as well as smilax and other climbing 

 vines. Heer considered the mean temperature indicated by 

 these plants of northern Greenland to have been not less than 

 55° F. ; though Frofe&sor Nathorst, the most distinguished 

 living authority on the plants of the polar lands, shows this 

 estimate to be certainly too high for the close of the period, 

 which was, however, warm enough for the ripening of walnuts 

 in 70° 25^ ^. L. Moreover, by this time fairly sharp polar 

 winters had set in. Supplementary evidence showing this 

 steady decline in Arctic Tertiary temperature has accumulated 

 from a series of localities fairly girdling the pole. The prin- 

 cipal ones are the Sabine Island on the east coast of Green- 

 land, Iceland, Spitzbergen and the new Siberian Islands. 



In brief the north polar regions were as yet markedly tropical 

 in Jurassic time, and less so by the close of the Cretaceous ; 

 whilst the several northern fossil florae indicate a steady, per- 

 sistent, unmistakable secular decline in temperature over the 

 entire polar area, culminating in the late Tertiary in arctic 

 conditions. 



That the rich vegetation of the various horizons represented 

 within the Arctic area forms the original source of most of the 

 plant families, which as the evidence shows spread synchron- 

 ously over Eurasia and America throughout Cretaceous and 

 Tertiary time, is a conclusion which we can scarce escape. 

 But as to the actual flrst home of the Dicotyls it would of 

 course on the basis of present knowledge be a gratuitous guess 

 to say that this was within the Arctic circle. The}^ may rather 

 be a legacy left over from the later generalized tropical periods, 

 these being characterized, as stated, by easy distribution. The 

 first Mono- and Dicotyls may hence never be assigned to any 

 particular region. 



It is, however, to be observed that the early Angiosperms, 

 which appear alike unheralded in the Cretaceous of Maryland 

 and Portugal, may really be younger than the plants of the 

 Greenland [Jrgonian (Kome beds). I only need note that the 

 belief in the similar age of these beds rests entirely on floral 

 evidence, and that equivalent florse in such widely separated 

 localities afford very insuflicient proof of synchronism. More- 

 over, in view of what we now know of soutliern migrations if 

 in the case of two quite similar but widely distant fossil faunge 

 or florae, one rests far to the north, it is likely, once the strati- 



