CLIMATIC VARIATIONS GEEGOEY. 343 



Islands; but in both cases the evidence shows that the coral faunas 

 were stunted in comparison with those of the contemporary seas to 

 the south. Numerous simple and simply branched corals, associated 

 with thick growths of calcareous algse, grow to-day in the northern 

 seas. Dead branches of Lophohelia are so common on one bank in the 

 Christiania Sound (latitude 58° N.) that it has been described as a 

 Pleistocene coral reef. Small nodules of corals, of reef-building 

 genera, such as Plesiastrcea^ live at present in the cold seas of south- 

 ern Australia, far to the south of the region of coral reefs. 



Hence I feel justified in repeating the view expressed in 1897, that 

 the evidence of the fossil corals from the Silurian rocks of Greenland 

 and Great Britain shows " that there was almost as great a difference 

 between the temperature of the sea in the areas as there is to-day." "^ 



The evidence of the fossil corals is supported by that of the arctic 

 marine faunas of all geological periods. Their most striking char- 

 acteristics in the past are their characteristics of to-day, and show 

 " that all through geological time the northern faunas have lived 

 under the blight of arctic barrenness." ^ 



THE EVIDENCE OF THE FOSSIL FLORAS. 



The fossil floras of the Arctic, as identified by Heer, have been used 

 as the basis of the attractively sensational theory that Greenland 

 enjoyed a tropical climate in Miocene times and a tropical or sub- 

 tropical climate in Cretaceous times. But the evidence so far adduced 

 appears to be quite insufficient to justify this view. The most char- 

 acteristically tropical of the plants claimed to occur in Greenland are 

 the palms; but the fossil arctic palms have now been dismissed as 

 based on erroneous identifications. Much weight has also been at- 

 tached to some fossil tree ferns of the genus Dicksonia^ from the 

 Cretaceous of Greenland. But the best-known living species of that 

 genus is Dicksonia antarctica^ which occurs in southern New Zealand; 

 and Dicksonia also lives on the high " Snowy Plains " of the Victo- 

 rian Highlands, where it is sometimes buried under snow for four or 

 five months in the year. Hence the existence of fossil tree ferns, espe- 

 cially of the genus Dicksonia, would certainly not imply tropical con- 

 ditions. Heer's identifications have been contemptuously rejected by 

 many later botanists, including Dr. Robert Brown, Dr. Starkie Gard- 

 ner, and Professor Nathorst. Most of Heer's determinations were 

 based upon leaves, which give no data for generic identification. Nor 

 does the existence of leaf beds in the Arctic prove anything more than 

 local geographical changes, for leaves grow with remarkable rapidity 

 and luxuriance within the Arctic Circle, under the influence of the 



-^ Op. cit, Nature, Vol. LVI, 1897, p. 352. 

 6 Ibid., p. 352. 

 88292— SM 1908 23 



