442 FLORA OF THE LARAAtlE GROUP. 



merely sum- up the data contained in these more detailed entries and 

 exhibit the three formations side by side in compact form for ready 

 coini)aris()ii. 



To this are added eleven columns for the purpose of indicating the 

 vertical range of both the genera and the species. The iirst of these, 

 in whidi the letter referring to the foot-note is substituted for tlie con- 

 ventional sign, shows those forms which occur below the Cretaceous, 

 the footnotes showing the formations in which found. The headings 

 of the other ten columns sufftciently explain themselves. 



The geogra])hical distribution of living genera, so far as practicable, 

 and of genera closely allied to extinct ones, is also given in fbot-uotes, and 

 the number of si)ecies of living phenogamous genera, as estimated by 

 the highest botanical authorities, is indicated by figures in parenthesis. 

 The importance and significance of this feature will be discussed in the 

 proper place. 



