GEOLOGICAL CLIMATE IN HIGH LATITUDES. 357 



from the shores of the Arctic Ocean to the coasts of Bolivia, were 

 everywhere largely the same ; always enough of identical species to 

 show that arctic and tropical environments were essentially alike. It 

 seems, if possible, still more incredible that in later times say, in the 

 Miocene species which originated in Spitzbergen and upper Green- 

 land could migrate to low latitudes, and still show no change in spe- 

 cific characters. 



It certainly was to be expected that conditions so unlike I refer, 

 now, only to the long days and nights should have been attended by 

 widely diverse plant-life. 



The belief that such would have been the case is strengthened by 

 the fact noticed by Mr. H. C. Watson, and quoted approvingly by 

 Mr. Darwin in his " Origin of Species," that, " in receding from polar 

 toward equatorial latitudes, the Alpine or mountain floras really be- 

 come less and less arctic." 



But, were they truly arctic, and identical with those now in Spitz- 

 bergen, such floras, accustomed to a hibernation of nine months, might 

 well be indifferent as to where that time was spent, whether in the 

 cold and continuous darkness of an arctic night, or in the cold of a 

 winter on a low-latitude mountain-top. On the other hand, the plants, 

 e. g., of the Carboniferous, were not arctic plants, but were warm-tem- 

 perate, if not tropical, and there was no arctic cold, but "a warm, 

 moist, equable atmosphere,"* in which they "flourished luxuriantly."! 

 Another corroborative fact is found in the peculiar structure of certain 

 post-glacial arctic trees. A conifer, found standing in latitude 72, 

 and of post-glacial origin, was brought to England by Sir E. Belcher, 

 where Sir William Hooker made a microscopical examination of its 

 structure. He found that it differed remarkably from any other coni- 

 fer with which he was acquainted. Each annual ring consisted of two 

 zones of tissue : the inner zone was narrow, of a dark color, formed 

 of more slender, woody fibers, with few or no disks upon them ; the 

 outer zone was broader, of a pale color, and consisted of ordinary 

 tubes of fiber of wood marked with disks such as are common to all 

 coniferae. These characters he found in all parts of the wood. They 

 suggest, as he says, the annual recurrence of some special cause that 

 modified the first and last formed fibers of each year's deposit, and 

 this cause, he thinks, is found in the peculiar conditions of an arctic 

 climate, where the days were at first very short, a few hours only 

 of sunshine. Then the first and imperfectly developed fibers were 

 formed. As the days grew longer and longer, and the solar rays at 

 last became continuous, the woody fibers became more perfect, and 

 were studded with disks of a more highly organized structure than 

 are usual in the natural order to which this tree belongs. % 



Since Spitzbergen is nearly 5 farther north, such or similar effects 

 ought to show themselves there in greater intensity in the conifers of 



* Dana. f Lyell. % See tnis account in Croll's "Climate and Time," pp. 264, 265. 



