Variation, Geographical Distribution, and Succession. 93 



An elaborate paper on the vegetation of the Tertiary period, 

 in the south-east of France, by Count Gaston de Saporta, pub- 

 lished in the 'Ann. So. Nat.' in 1862 (vol. xvi. pp. 309-344) 

 which we have not space to analyse, is worthy of attention from 

 the general inquirer, on account of its analysis of the Tertiary 

 flora into its separate types — Cretaceous, Austral, Tropical, and 

 Boreal — each of which has its separate and difl'erent history; 

 and for the announcement that " the hiatus which, in the idea 

 of most geologists, intervened between the close of the Creta- 

 ceous and the beginning of the Tertiary appears to have had 

 no existence, so far as concerns the vegetation ; that in general 

 it was not by means of a total overthrow, followed by a complete 

 new emission of species, that the flora has been renewed at each 

 successive period ; and that while the plants of Southern Europe 

 inherited from the Cretaceous period more or less rapidly dis- 

 appeared, as also the austral forms, and later the tropical types 

 (except the Laurel, the Myrtle, and the Chamcerops humilis), the 

 boreal types, coming later, survived all the others, and now 

 compose, either in Europe, or in the north of Asia, or in North 

 America, the basis of the actual arborescent vegetation. Espe- 

 cially " a very considerable number of forms nearly identical 

 with Tertiary forms now exist in America, where they have 

 found, more easily than in our [European] soil (less vast and 

 less extended southward), refuge from ulterior revolutions." 

 The extinction of species is attributed to two kinds of causes — 

 the one material or physical, whether slow or rapid, the other 

 inherent in the nature of organic beings, incessant, but slow, in 

 a manner latent, but somehow, assigning to the species, as to the 

 individuals, a limited period of existence, and, in some equally 

 mysterious but wholly natural way, connected with the develop- 

 ment of organic types — "by typ)e meaning a collection of 

 vegetable forms constructed upon the same plan of organization, 

 of which they reproduce the essential lineaments with certain 

 secondary modifications, and which appear to run back to a 

 common point of departure." 



In this community of types, no less than in the community 

 of certain existing species, Saporta recognizes a prolonged ma- 

 terial union between North America and Europe in former times. 

 Most naturalists and geologists reason in the same way, some 

 more cautiously than others ; yet perhaps most of them seem 

 not to perceive how far such inferences imply the doctrine of the 

 common origin of related species. 



For obvious reasons such doctrines are likely to find more 

 favour with botanists than with zoologists. But with both the 

 advance in this direction is seen to have been rapid and great, 

 yet to us not unexpected. We note also an evident disposition, 



