WARD.J VEGETATION OF THE LARAMIE AGE. 437 



out of the inaiiner in which the Laramie sea was produced and the 

 changing constituents of its waters. But all the other difficulties pre- 

 sent themselves here as in the case last considered. While the vege- 

 table remains seem to be more harmonious in pointing to a somewhat 

 later period of time for their deposition than do those of vertebrate 

 animals, the impropriety of inferring absolute synchronism from sub- 

 stantial agreement of forms is here even greater than in the other case. 

 Taking the present -flora of the globe as a criterion, we find that the 

 geographical distribution of plants is more uneven than that of animals. 

 Floral realms are more numerous and distinct than faunal realms, and 

 the more serious obstacle that some areas furnish types representing 

 less developed floras than others exists here as in the case of animals. 

 The Proteaceous and Myrtaceous flora of Australia may be regarded as 

 rudelv corresponding to its marsupial fauna. 



• It is true that the paleontological doctrine of synchronism already 

 stated is supported, as against the facts of geographical distribution, 

 by the well established principle that older faunas and floras were char- 

 acterized by less variety and greater uniformity of distribution over 

 the earth's surface, which is verified in a remarkable manner by the 

 well known uniformity of the flora of the Carboniferous epoch at all 

 points where it has been discovered. And Baron Ettingshauseu has 

 shown that this principle continued in operation dowu to the close of 

 the Tertiarv age, though, of course, in a reduced degree, so that the 

 present extraordinary variety in the floras of ditterent countries must 

 be largely attributed to the agency of the successive glacial epochs 

 which\ave occurred since Tertiary time in driving the floras south- 

 ward and out on the southern plains to be destroyed on the return of 

 warmer climatic influences or compelled to intrench themselves upon 

 the summits of the mountain ranges, while new and constantly vary- 

 ing forms became developed to take their places in the lowlands. Still, 

 the uniformitariau law, that in its more general aspects the phenomena 

 taking place on the earth in past geologic ages were the same as those 

 which are still taking place, forbids us to assume that even as far back 

 as Laramie time the same or any very similar flora occupied ditterent 

 hemispheres of the globe. 



This much, however, cau be said in favor of the flora of the Laramie 

 group as attbrding data for the study of its deposits : that its remains 

 occur far more abundantly than do those of any of the other forms of 

 life. The low forest-clad shores and islands of the Laramie sea, which 

 probably extended back at many points into extensive lagoons aud vast 

 swamps, were peculiarly adapted for receiving, as its muddy waters 

 were for embedding, the various kinds of vegetable matter that found 

 their way into them. The swamps formed extensive beds of peat, and 

 vast marshes densely covered with cane, bamboo, and scouring rush 

 left thick annual accumulations of vegetable matter which, at points of 

 slow temporary subsidence, formed the coal beds. The plant beds which 



