372 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



Umbelliferae, Krameriaceae, Papilionaceae, etc., were relatively very 

 modern and their main evolutionary deployment seems to have been 

 largely Pleistocene and postglacial. The subject is much too large 

 for treatment in the present article, but a somewhat full discussion of 

 the geological history of the angiosperms will be found in the Pro- 

 ceedings of the American Philosophical Society, volume 53, pages 

 129-250, 1914. 



Fig. 26.— Diagram showing the geologic history and phytogeny of vascular plants. 



CONCLUSION. 



The mutual relationships of the various groups of vascular plants 

 that have been briefly discussed in the preceding paragraphs are 

 shown in figure 26, which aims to represent graphically their 

 phytogeny as understood by the writer and their relative importance 

 throughout geologic times. 



THE EVOLUTION OF FLORAS. 



STAGES OF PLANT EVOLUTION. 



Somewhat as in human history a long period of mythology pre- 

 ceded written history, so in a consideration of the history of the 



