112 



NATURE 



^Dec. 5, 1878 



As a contribution to the principles of geogi'aphical botany, 

 Comte Gaston de Saporta's essay, entitled " L'Anciennc Vegeta- 

 tion Polaire " (which appeared in the Coinptes Rendus of the 

 French International Geographical Congress) is a very suggest- 

 ive one, and, having regard especially to its author's eminence as 

 a geologist and palaeontologist, is sure to command attentive 

 study. Although it may be argued that neither solar nor terres- 

 trial physics, nor geology, nor palaeontology are in a sufficiently 

 advanced condition to warrant the acceptation as altogether es- 

 tablished truths of all conclusions advanced in it, still the array 

 of facts adduced in evidence of these conclusions is very imposing, 

 while the ability and adroitness with which they are brought to 

 bear on the subject are almost worthy of the great French genius 

 whose speculations from the starting-point of the theory, which is 

 that life appeared first in the northern circumpolar area of the 

 globe, and that this was the birthplace of the first and of all 

 subsequent floras. 



I should premise that Count Saporta professedly bases his 

 speculations upon the labours of his friend. Professor Heer, 

 whose reasonings and speculations he ever puts forward with 

 generous appreciation, while differing from him wholly on the 

 subject of evolution, of which he is an imcomprising supporter, 

 Professor Heer holding to the doctrine of the sporadic creation of 

 species. 



In his " Epoques de la Nature" Buffon argues that the cool- 

 ing of the globe, having been a gradual process, the polar regions 

 must have been the first in which the heat was sufficiently mode- 

 rate for life to have appeared upon it ; that other regions being 

 as yet too hot to give origin to organised beings, a long period 

 must have elapsed, during which the northern regions, being no 

 longer incandescent, as they and all others originally were, must 

 have had the same temperature as the most tropical regions now 

 possess. 



Starting from this thesis. Count Saporta proceeds to assume 

 that the termination ot the azoic period coincided with a cooling 

 of the water to the point at which the coagulation of albumen 

 does not take place ; and that then organic life appeared, not in 

 contact with the atmosphere, but in the water itself. Not only 

 does he regard life as originating, if not at the North Pole, at 

 least near to it, but he holds that for a long period life was active 

 and reproductive only there. In evidence of this he cites various 

 geological facts, as that the older, and at the same time the 

 richest, fossiliferous beds are found in the cool latitudes of the 

 North, namely in lats. 50° to 60", and beyond them. It is in the 

 North, he says, that Silurian formations occur, and though they 

 extend as far south as lat. 35° N. in Spain and America, the most 

 characteristic beds ai^e found in Bohemia, England, Scandinavia, 

 and the United States. The Laurentian rocks again, he says, 

 reach their highest development in Canada, and palaeozoic rocks 

 cover a considerable polar area north of the American great lakes, 

 and appear in the coasts of Baffin's Bay, and in parts of Green- 

 land and Spitzbergen. It is the same with the Upper Devonian 

 and marine carboniferous beds preceding the coal formations ; 

 these extend to 76° N. in the polar islands and in Greenland, and 

 to' 79° N, in Spitzbergen, and he adds that M. d'Archiac has long 

 ago remarked that, though so continuous to the northward, the 

 coal-beds become exceptional to the southward of 35° N. 

 Hence Count Saporta concludes that the climatic conditions 

 favourable to the formation of coal were not everywhere pre- 

 valent on the globe, for that while the southern limit of this 

 formation may be approximately drawn, its northern must have 

 extended to the Pole itself. 



I pass over Saporta's speculations regarding the initial condi- 

 tions of terrestrial life, which followed upon the emergence of the 

 earlier stratified rocks from the Polar Ocean, and proceed to his dis- 

 cussion of the climate of the carboniferous epoch as indicated by the 

 characters of its vegetation, and of the conditions under which 

 alone he conceives this can have flourished in latitudes now con- 

 tinuously deprived of solar light throughout many months of the 

 year. In the first place, he accepts Heer's conclusions (founded 

 on the presence of a tree-fern in the coal measures specifically 

 similar to an existing tropical one), that the climate was warm, 

 moist, and equable, and continuously so over the whole globe, 

 without distinction of latitude. This leads him to ask whether, 

 when the polar regions were inhabited by the same species as 

 Europe itself, they could have been exposed to conditions which 

 turned their summers into a day of many months' duration, and 

 their winters into a night of proportional length ? 



A temperature so equable throughout the year as to favour a 

 rich growth of cryptogamic plants, appears, he says, to be at 



first sight incompatible with such alternating conditions (as a 

 winter of one long night and a summer of one long day) ; but 

 equability, even in high latitudes, may be produced by the effect 

 of fogs due to southerly warm oceanic currents, such as bathe 

 the Orkneys and even Bear Island (in lat. 75° N.), and render 

 their summers cool and winteis mild. To the direct effects 

 of these he would add the action of such fogs in preventing 

 terrestrial radiation, and hence the cold this produces ; and he 

 would further efface the existing conditions of a long winter 

 darkness by the hypothesis that the solar light was not, during 

 the formation of the coal, distributed over the globe as it now 

 is, but was far more diffusive, the solar body not having yet 

 arrived at its present state of condensation. 



That the polar area was the centre of origination for the 

 successive phases of vegetation that have appeared in the globe 

 is evidenced, under Count Saporta's view, by the fact that all 

 formations, carboniferous, Jurassic, cretaceous, and tertiary, 

 ai-e alike abundantly represented in the rocks of that area, and 

 that, in each case, their constituents closely resemble that of 

 much lower latitudes. The first indications of the climate cooling 

 in these regions is afforded by Coniferce, which appear in the polar 

 lower cretaceous formations. These are followed by the first 

 appearance of dicotyledons with deciduous leaves, .which again 

 marks the period when the summer and winter season first 

 became strongly contrasted. The introduction of these 

 (deciduous-leaved trees) he regards as the greatest revolution in 

 vegetation that the world has seen ; and he conceives that once 

 evolved they increased, both in multiplicity and diversity of 

 form, with great rapidity, and not in one spot only, and 

 continued to do so down to the present time. 



Lastly, the advent of the miocene period, in the polar area, 

 was accompanied with the production of a profusion of genera, 

 the majority of which have existing representatives which must 

 now be sought in a latitude 40° further south, and to which 

 they were driven by the advent and advance of the glacial cold ; 

 and here Count Saporta's conclusions accord with those of 

 Prof. A. Gray,' who first showed, now twenty years ago, 

 that the representatives of the elements of the United States 

 flora previously inhabited high northern latitudes, from which 

 they were driven south during the glacial period. 



Perhaps the most novel idea in Count Saporta's 'essay is that 

 of the diffused sunlight which (with a densely clouded atmo- 

 sphere), the author assumes to have been operative in reducing 

 the contrast between the polar summers and winters. If it be 

 accepted it at once disposes of the difficulty of admitting that 

 evergreen trees survived a long polar winter of total darkness, 

 and summer of constant stimulation by bright sunlight ; and if, 

 further, it is admitted that it is to internal heat we may ascribe • 

 the tropical aspect of the former vegetation of the polar region, 

 then there is no necessity for assuming that the solar system at 

 those periods was in a warmer area of stellar space, or that the 

 position of the poles was altered, to account for the high tempera- 

 ture of pre-glacial times in high northern latitudes ; or, lastly, 

 that the main features of the great continents and oceans were 

 very different in early geological times from what they now are. 

 Count Saporta's views in certain points coincide with those of 

 Prof. Le Conte of California, who holds that [the uniformity 

 of climates during earlier conditions of the globe is not explicable 

 by changes in the position of the poles, but is attributable to a 

 higher temperature of the whole globe, whether due to external 

 or intern al'causes, to the gi-eat amount of carbonic acid and water 

 in the atmosphere, which would shut ;in and accumulate the 

 sun's heat, according to the principles discovered by Tyndall and 

 applied by Sterry Hunt in explanations of geological times, 

 and possibly to a warmer' position in stellar space, a more 

 uniform distribution of surface temperature, and a different dis- 

 tribution of land and water. ^ 



Before ' Count Saporta's essay had reached this ;C0untry - 

 another continuation of the subject of the origin of existmg 

 floras had been communicated to our own Geographical Society, 

 by Mr. Thiselton Dyer in a lecture on " Plant Distribution as a 

 Field for Geographical Research." Mr. Thiselton Dyer's order 

 of procedure is the reverse of Count Saporta's, and his method 

 entirely different. He first gives a very clear outline of the 

 distribution of the principal existing floras of the continents and 



iProfessor Jos. Le Conte, in Nature, vol. xviii. p. 668. 



2 Count Saporta's essay was presented to the International Congress of 

 Geographical Science which met in Paris in 1875, and was not received m 

 England till the autumn of 1878, though it bears date of 1S77 on the title 



