414 Progress of Natural History^ 



abundant, and there is a dearth of dicotyledons in all three ; 

 but in the fourth is a remarkable predominance of dicotyle- 

 dons, and a similarity to the vegetables of the present day. 

 Thus, as in the animal kingdom, an affinity may be traced 

 between each succession and the state of vegetation in the 

 different zones of the present globe. The Flora of the first 

 period approaches to that of the small islands between the 

 tropics, and far from continents ; which induces the author to 

 think, that during this period the temperature of the earth was 

 higher, and that it was formed of small islands, scattered in a 

 vast ocean, and that no great continent existed ; a result which, 

 in other respects, agrees with the disposition of coal form- 

 ations, and at which Deluc and others have arrived by different 

 means. The second and third periods have some of the cha- 

 racters of the larger islands and the coasts ; and, lastly, the 

 fourth period, or tertiary formation, is analogous to the vege- 

 getables of the temperate zones, especially the forests of Europe 

 and North America. Many of these vegetables have been 

 developed before we find any traces of animals ; but, as we 

 advance, we perceive cold-blooded animals ; but it is only in 

 the middle of the fourth period that animals with warm blood 

 are found in any number, and their appearance coincides in a 

 remarkable degree with the multiplication of dicotyledons. 

 With such facts before him, the young author has been un- 

 able to resist the temptation of trying to account for these 

 wonderful vicissitudes, and he thinks they are owing to the 

 action of these vegetables upon the atmosphere. He sup- 

 poses that the carbon now employed in organic life was at 

 first, under the form of carbonic acid, an integral part of the 

 atmosphere, from which it was extracted by vegetable ab- 

 sorption. " Being surcharged with this acid," says M. Adolphe 

 Brongniart, " the atmosphere was as favourable to the rapid 

 growth of plants, as it was injurious to that of animals with 

 warm blood ; and it is before these animals show themselves, 

 that we find these enormous masses of vegetables. Animals 

 with cold blood do not require so pure an air, and have 

 appeared when much of this carbonic acid has been absorbed ; 

 and the animals with warm blood have only existed when the 

 air has been more completely purified by the long continued 

 action of vegetation, and especially vegetation consisting of 

 large forests, spread over vast continents." 



In that portion of M. Cuvier's report devoted to Vegetable 

 Physiology and Botany is an account of a new discovery made 

 by M. Dutrochet, which has been deemeji so new and im- 

 portant, that the Academy has voted him the physiological 

 prize founded by M. de Monthyon. M. Dutrochet calls his 



