No.1.] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 4J 



latter country, and of anotlier in Tibet. From our western Uoras it is- 

 totally absent. 



PLTJJMBAGlNACEii^. — In tliis comitry very few, and coMlined to the sea- 

 coasts; are not noteworthy. 



PremulaceyE. — jSTeed little mentiou, most of the genera being amphi- 

 gaean and widely distributed over the country, although few in species, 

 many of them alpine or alpestrine. The most peculiar genus, Dode- 

 catheoii, spans the continent in very various forms, which seem to be 

 connected into one species. The true species of Lysimachia are only on 

 the Atlantic side, and so mainly is the peculiar genius Steironeyna^ 

 although the commonest species extends northward to the Pacific. 



SapotacEyE. — This is one of several orders which, although mainly 

 tropical, have temperate representatives in the Atlantic United States, 

 where there are at least three species of Bumelia. 



EBENACEiE.— Are in similar case. Diofipyros Virginiana, our Persim- 

 mon, extends north to latitude 41°, and barely crosses the Mississippi. 

 A Texan species lies beyond our line. Westward the order is wanting. 



Styracace^. — Are found on both sides of the continent, but not at 

 all in the intermediate regions. The order is one of those that affect 

 the eastern side of continents. Accordingly, the Atlantic flora has- 

 three genera {Symplocos, Halesia, Styrax) and eight species; the Pacific 

 flora only a single Styrax. 



Oleace^. — Are fairly well represented in the Atlantic flora by six 

 or seven species of Fraxinus, a few of Forefstiera. a Chionanthn.'i, and an 

 Osmantlius ; two species of Fraxinus are the sole representatives in the 

 Pitciflc flora. The wide intervening region has none except a FraxiiiuSy 

 with simple leaves, on the southern border, where also flourish one or 

 two species of Forestiera and of the Texano-Mexican genus Menodora. 



Apocy'nace^Ti:. — The two species of Apocynum make a part of all three 

 floras ; the Pacific has a peculiar genus, Cycladenia ; the Atlantic, a plant 

 referred to the Northeastern Asian genus TracheIos])ermum, and Amsonia 

 (which is also Japanese"), the latter reaching the southern borders of 

 the Great Basin. 



AscLEPi ADAGES — Most of Asclepias is Korth American, and the spe- 

 cies, as to number, are not very unequally divided between the three floras, 

 at least if New Mexico and xVrizona be taken into the account. This 

 southern frontier and the countrj" beyond is rather rich in the order. The 

 Pacific flora has three sjiecies nearly related to AsclepiaH ; one of them 

 is made the type of a peculiar genus, Schisonotns, the otlier two are re- 

 ferred to the chiefly' African genus Gomphocarpus. The Atlantic flora 

 divides with that of the plains up to the Eocky Mountains the genera 

 Acerates and Asclepiodora^ with tropical parts of America the genus 

 Enslenia^ and is also rich in Gonolobus; and it monopolizes the genera 

 Podostigma and Anantherix. 



LoGANiACE^. — As our species of Buddleia and the genus Emorya 

 belong to the Texano-Arizonian region, it may be said that this order 



