42 FLOKA OF WASHINGTON AND VICINITY. 



the second place, if it should be thought that from its intermediate 

 location between the southern and the northern sections of the country 

 our flora should naturally be the more rich in species, it may be satis- 

 factorily urged on the other hand that while we have only an inland 

 territory, Essex County has both an inland and a maritime territory. 

 Could our range be extended to embrace even a small extent of sea- 

 coast, the number would thereby be very largely increased. 



As a final statistical exhibit more comprehensive in its scope, and 

 from a difierent point of view, I give below a table in which our local 

 flora is compared not only with the floras above named, but with sev- 

 eral others in America. As these several floras not only overlap to 

 considerable extent, but also differ widely in the total number of plants 

 embraced by each, it is evident that a numerical comparison would con- 

 vey a very imperfect idea of the variety in their essential characteristics. 

 It is therefore necessary to reduce them to a common standard of com- 

 parison, which has been done by disregarding the actual numbers and 

 employing only the percentage which each group compared bears to the 

 total for each respective flora. The relation of the several groups to 

 the total vegetation of each flora is thus clearly brought out, and a 

 comi^arison of the percentages of the same group in the different areas 

 displays in the clearest manner i)ossible the relative predominance or 

 scantiness of the grouj) in each flora. Upon this must depend, in so far 

 as botanical statistics can indicate it, the fades of each flora — its pecu- 

 liarities and its characteristics. As in previous comparisons, the table 

 is restricted to Phoenogamous and vascular Cryptogamous plants, and 

 the same groups are employed, except that the large genera are omit- 

 ted, while the number of orders is increased to the 23 largest of this 

 flora, which is taken as the basis of comparison, and they are arranged 

 in the order of rank with reference to it. 



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

 braced in each, are as follows : 



1. Flora of Washington and vicinity 1,249 



2. Flora of Essex County, Mass 1, 324 



3. Flora of the State of Illinois 1,542 



4. Flora of the Northeastern United States 2, 365 



5. Flora of the Southeastern United States 2, 696 



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



7. Plants collected by the Fortieth Parallel Survey 1, 254 



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



For the flora of Illinois (No. 3), and also for that of the Northern 

 United States east of the Mississippi (No. 4), I have used without veri- 



