No. 1.] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 49 



Ulmace^. — There are four fine Elin trees in the Atlantic flora, and 

 one farther southwest, also the Planer a ; none of these in the Ko(;ky 

 Mountain or the Pacific floras; Celtis, either a form of the common 

 eastern or a j^eculiar species, extends into the Eocky Mountains and even 

 to Oregon. 



CANNABiNEiE. — The cominon Hop of the Old World is indigenou.s in 

 the Atlantic States and in the Rocky Mountains ; the other species is 

 Oh ino- Japanese. 



MoiiE^. — Moms rwZ^ra is of the Atlantic States, extending far south- 

 ward and thence westward, perhaps passing into a small-leaved species. 

 Madura aurantiaca, the Osage Orange, belongs to the northwestern bor- 

 ders of the Atlantic district. None in the western floras. 



PLATANACEiE. — There is one Atlantic and one Californian Platanus; 

 but none intervening, except on the Mexican borders. 



Leitnerie^. — The anomalous Leitneria, of Florida, is of a single spe- 

 cies, of wholly obscure affinity. 



JuGLANDACE^T]. — Juglans cinerea and J. nigra or the Walnut trees 

 of the Atlantic flora, J. California of the Pacific ; Carya is of seven 

 species, restricted to the Atlantic flora. 



CupuLiFEE^. — Are most fully represented in the Atlantic flora, are 

 prominent in the Pacific flora, but are wanting in the whole interior 

 region, excepting a Scrub Oak or two on the Eocky Mountains and their 

 accessories. There are twenty-one Oaks, two Chestnuts, and a Beech in 

 the Atlantic flora; nine Oaks and a Castanopsis in the Pacific flora; 

 one Oak in the Eocky Mountain flora, or perhaps more than one ; and 

 two or three others in the district between it and Mexico. 



CoRYLACE^. — An Ostrya and a Carpimis and two species of Corylus 

 represent this group in the Atlantic flora. The two western floras want 

 all but one of the latter, which traverses the continent. 



Betulace^. — Are represented in the Atlantic flora by seven Birches 

 and three Alders. One of the smaller Birches and perhaps one of the 

 Alders, extends over to the Pacific flora, along with another Rocky 

 Mountain Birch, and two or three Alders are added. 



Myricace^. — The amphigaean Myrica Gale is of the Atlantic flora ; 

 one A'^ery like it in the Pacific. Of the Bayberry 3fyricce, there are one 

 or two on the Atlantic, and another on the Pacific coast. The Camp- 

 fonia is peculiar to the Atlantic flora. 



Salicine^. — There are about fifteen Willows indigenous to the At- 

 lantic States, nineteen in the Californian flora, very few of them iden- 

 tical ; the Eocky Mountains have a few of these and one or two more ot 

 alpine type. There are six Poplars in the Atlantic States ; three or four 

 in California and Oregon; one or two in the intermediate country, be- 

 sides P. tremuloides, which, passing along the mountains, is common to 

 all three floras. 

 The Gymnospermece may best be exibited under the particular groups. 

 G-N-ETACis^.— Ephedra, the only extratropical genus, is absent from 



4 GB 



