34 



FLORA OF WASHINGTON AND VICINITY. 



IX. STATISTICAL VIEW OF THE FLORA. 



In order to present a clear view of the general character of the vege- 

 tation of the District of Golnmbia and the adjacent country, I have 

 made a somewhat careful analysis of the larger groups and families, and 

 comparison of them not o nly with each other but with the same groups 

 and families in larger areas and other local floras. The general results 

 are presented below. 



It is important to remark that in all enumerations it is not simply the 

 number of species as at present recognized, but the number of different 

 plants (species and varieties) that is employed. The reason for doing 

 this is, that in very many cases well-marked varieties are eventually 

 made species, and if two plants really differ there is little probability 

 that they will ever be merged into one species without that difference 

 being indicated by some difference of name. The aim has therefore 

 been to take account of the number of plants without regard, to the 

 manner in which they are named. 



The whole number of vascular plants now known to this flora, as cat- 

 alogued in the list appended to this paper, is 1,249, and these belong 

 to 527 different genera, or about 2^ species to each genus. These are 

 distributed among the several systematic groups as follows: 



Series, Classes, and Divisions. 



Polypetalae . 

 GamopetaliB 



Total DicblaraydesB... 

 Monochlamydeai (Apetalse) . 



Total Dicotyledons . . 



Monocotyledons 



Gymnospermaj (Coniferae) 



Total Phanogamia.. 

 Cryptogamia 



Total Vascular Plants 



The pevccntages of the total are as follows : 



Polypetalaj 



Gamopetalaj 



Total DichlamydeiB... 

 Monocblaniydeai (Apetala)) . 



Total Dicotyledons 



Monocotyledons 



Gymnospcrmae (Coniferae) .. 



Total Ph:enogamia 



Crj-ptogamia 



C 



-^Y f. 



f\ 



Genera. 



Species and 

 varieties. 



