PHILOSOPHICAL SOCIETY OF WASHINGTON. 103 



five, the differences are well marked in nearly all the groups, and 

 in most of the large orders. These are what express statistically 

 the essential characteristics of the northern as contrasted with the 

 southern flora. It is also obvious that the figures in column six 

 will, in most cases, express the mean between these two extremes. 

 To obtain the true position of our flora, it is necessary to observe 

 toward which of these extremes it most nearly approaches, and 

 whether it falls on the northern or southern side of the mean estab- 

 lished by column six. In instituting this comparison, we perceive 

 at the outset, that in the Polypetalous division, it falls so far on the 

 southern side as to come within four tenths of one per cent, of being 

 identical with the flora of the Southern States. In the Garnopetalce, 

 however, it agrees quite closely with the flora of Northern States, 

 so that in the Dichlamydeoe as a whole, it coincides very well with the 

 , mean for both sections. The Monochlamydece agree better with 

 those of the Southern States and the total Dicotyledons fall largely 

 on the southern side of the mean. The Monocotyledons also fall 

 somewhat on the southern side, while the Gymnosperms are below 

 the mean which here corresponds with the southern flora. This 

 leaves the total Phsenogams, occupying an intermediate position. 

 The Cryptogams are also very nearly intermediate, though ap- 

 proaching the northern side. 



Considering next the relations of the large orders, we find that 

 in the Compositce our flora is northern in aspect. In the Graminece 

 it is very exceptionally rich, surpassing all the larger areas and 

 approaching that of Essex county, Massachusetts. In the Cyper- 

 acece, which are peculiarly typical "for the purpose, on account of 

 being indigenous in all the floras, it does not correspond at all, 

 either with the northern section or with the average of both sec- 

 tions, but does agree very closely with the exceptionally meager 

 representation of the southern flora. The Leguminosce are here 

 northern in aspect, the Rosacece, like the Graminece, exceptionally 

 rich, far exceeding either section, as is also the case with the 

 Labiatce and the Cruciferce. The ferns are northern in their degree 

 of representation, as are the Ranunculacece while the Ericaceae and 

 Scrophulariacece are southern. The Cupuliferce again are anomal- 

 ous and tower above all other floras. The Liliacece are southern, as 

 are also the Orchidacece. The Polygonacece are in excess, and in so 

 far southern in aspect, while the Umbelliferce, also in excess, denote 

 a northern inclination. The Caryophyllacece are remarkable for 



