FLORA OF WASHINGTON AND VICINITY. 



41 



noteworthy that our flora exceeds that of Essex County most in the 

 Compositw, Leguniinoscc, and CupuliferWj and next to these in the Scroplm- 

 lariacea', Labiatcv, and Cruc>fera\ Our comparatively poorest orders are 

 the Cyperacem, Bosacew, Uricacecc, and Filices. 



Comparing in like manner the 15 large genera enumerated on page 35, 

 we are able to see still more definitely wherein the two floras differ: 



Genera. 



1 Carex 



2 Aster 



3 i Panicum 



4 Solidago 



5 I Quercus 



6 Polygonum . . 



7 ' Dcsmodium . 



8 i Salix 



9 Juncus 



10 i Viola 



11 Cyperus 



12 j Ranunculus. 



13 Eupatorium . 



14 Heiianthus.. 



15 i Asclepias . . . 



The total number of species and varieties represented by these 15 

 genera is thus considerably larger in the Washington flora (271) than 

 in that of Essex County (253) ; but whereas they are the absolutely 

 largest genera here, this is not the case there. The genus Potamogeton 

 numbers 23 in Mr. Eobinson's catalogue, and the genus Scirpus 14, while 

 several others probably exceed 10. Those in the above list falling 

 below 10, the lowest on the Washington list, are Desmodium (7), Eupa- 

 torium (7), Asclepias (7), and Heiianthus (5). Those in which the Essex 

 flora exceeds theWashington flora are Carex, Aster, Solidago, Polygonum, 

 Salix, and Ranunculus, though Carex, Solidago, and Cyperus may be re- 

 garded as equal in the two floras, and Juncus is exactly equal. In Quer- 

 cus, Desmodium, Eupatorium, Heiianthus, and Asclepias, the Essex flora is 

 poor, only amounting in the second and fourth named to half the num- 

 ber found here. 



Relative to the above comparisons in general it may be remarked, 

 first, that the flora of Essex County, Massachusetts, is much more 

 thoroughly and exhaustively elaborated than that of the District of 

 Columbia, lying as it does in the immediate center of botanical activity 

 in this country. This alone is probably sufticient to account for all the 

 difference in the number of species in the two localities, and it will prob- 

 ably be ultimately found that the two floras are very nearly equal. In 



