PHILOSOPHICAL SOCIETY OF WASHINGTON. 



97 



next to these in the Scrophulariacece, Labiatce and Cruciferce. Our 

 comparatively poorest orders are the Cyperacece, JRosacece, Ericaceoz 

 and Filices. Comparing in like manner the fifteen large genera 

 enumerated on page 90 we are able to see still more definitely 

 wherein the two floras differ. 



Large Genera. 



1. Carex 



2. Aster 



3. Panicum 



4. Solidago 



5. Quercus 



6. Polygonum 



7. Desmodium 



8. Salix 



9. Juncus 



10. Viola 



11. Cyperus 



12. Ranunculus 



13. Eupatorium 



14. Helianthus. 



15. Asclepias 



Number of Species 

 and Varieties. 



O 



W 



tt 



The total number of species and varieties represented by these 

 fifteen genera is thus considerably larger in the Washington flora 

 (271,) than in that of Essex county, (253 ;) but whereas they are 

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

 genus Potamogeton numbers 23 in Mr. Robinson's Catalogue, and 

 the genus Scirpus 14, while several others probably exceed ten. 

 Those in the above list falling below ten, the lowest on the Wash- 

 ington list, are Desmodium (7,) Eupatorium (7,) Asclepias (7,) and 

 Helianthus (5.) Those inwJbich the Essex flora exceeds the Wash- 

 ington flora are Carex, Aster, Solidago, Polygonum, Salix and Ran- 

 unculus, though Carex, Solidago and Cyperus may be regarded as 

 equal in the two floras, and Juncus is exactly equal. In Quercus, 

 Desmodium, Eupatorium, Helianthus and Asclepias, the Essex flora 

 7 



