PHILOSOPHICAL SOCIETY OF WASHINGTON. 99 



The several floras compared with the total number of plants em- 

 braced in each, are as follows : 



i. Flora of Washington and vicinity r > 2 49 



2. Flora of Essex county, Massachusetts 1,324 



3. Flora of the State of Illinois.. x ,54 2 



4. Flora of Northeastern United States 2,365 



5. Flora of Southeastern United States 2,696 



6. Flora of Eastern United States (= 4 -f- 5) 4,034 



7. Plants collected by the Fortieth Parallel Survey ^254 



8. Plants collected by Lieut. Wheeler's Survey 1,535 



For the flora of Illinois, (No. 3,) and also for that of the Nor- 

 thern United States, east of the Mississippi, (No. 4,) I have used, 

 without verification, the figures of the Catalogue of the Plants of 

 Illinois, 1876, prepared by Mr. Harry N. Patterson, as summarized 

 in the preface. In the former case, the introduced species are in- 

 cluded, but the varieties seem to be excluded. In the latter case, as 

 stated by Mr. Patterson, the introduced species are excluded, as are 

 also doubtless the varieties. 



For the flora of the Southern United States, east of Mississippi, 

 (No. 5,) which I have compiled from Dr. Chapman's Flora of the 

 Southern States, indigenous species are alone taken, in order to make 

 it conform as nearly as possible to the flora of the Northeastern 

 United States, .(No. 4.) 



The plants collected by the Fortieth Parallel Survey, (No. 7,) 

 and those collected on Lieut. Wheeler's' Survey, (No. 8,) are intro- 

 duced rather as a means of contrasting the Eastern with the 

 Western portions of the continent, than as a proper part of the 

 comparative botanical statistics of this vicinity. The former of 

 these collections was very thoroughly and carefully made by an 

 energetic and experienced botanist, Mr. Sereno Watson, and derives 

 1 its chief value from this fact. It embraces, however, a territory 

 having a somewhat special character from a botanical point of view, 

 viz : in general terms, the Great Basin between the Rocky Mount- 

 ains and the Sierra Nevada, and the High Plateaus and mountains 

 immediately adjacent, (Wasatch, Uintas, Sierras,) with a restricted 

 range north and south. The data are taken from the summary of 

 the work prepared by Mr. Watson, and found on page XIV of the 

 Report. The collections embraced in the Report of Lieut. Wheeler's 

 Survey, on the other hand, were made by numerous collectors, some 

 of them amateurs, and were scattered over a very wide extent of 



