^0.1.] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 37 



<)fiZte hardly crosses the A.lleghanies ; the singlG Liquiflamhar in aqnuWj 

 of eastern range, thougn it extends into and through ]\Ioxico. 



HaloeagevTi;. — Are of small account. The auiphigjuan Ilippuris and 

 one or two of MyriophylluniGxtQnd across tlie continent northward; but 

 Froserpinaca, of two species, is restricted to the Atlantic flora. 



Melastomacbje. — Rhexia of the Atlantic flora alone represents this 

 great typical order in a temperate climate. 



Li^TiiRACEyE.— Largely tropical or subtropical ; two or three species of 

 A7n mannia and Lythrum are of wide distribntion ; and the Atlantic States 

 have a Cupliea and a Nescva^ Eastern South American types. The pecu- 

 liar genus DidipUs is nearly an aquatic Ammannia. 



Onageace^. — A largely American order. Epilobium, a cosmopoli- 

 tan genus, is most diversified in the Pacific flora. Clarlda, BoisduvaUa, 

 UulobuSj Eucliaridium, and Heterogaura are restricted to it ; Zauschneria, 

 Oayojjhytum, ami the principal Avealth of the great genus CEnothera,to 

 the Eocky Mountain and Pacific region ; Gaura and Stenosiphon mainly 

 to the great plains east and southeast of the Eocky Mountains. Lud- 

 tvifjia and the diurnal yellow-flowered (Enotherw, with clavate capsules, 

 are Atlantic types. Godetia is one of the most characteristic of Pacific- 

 coast genera, but also Chilian. 



Loasace^. — Are wholly American, with the odd exception of a South 

 African genus of a single species. It is wanting from the Atlantic flora, 

 but well represented in the Eocky Mountain and Pacific floras by various 

 species of Mentzelia. The most showy vespertine species, M. ornata and 

 M. nuda, are very characteristic on the plains between the Mississippi 

 aud the Eocky Mountains. JEucnide and Petalonyx are Texan o-Arizo- 

 niau genera. 



TuENERACEiE. — Tropical plants ; one or two species of Turnera on 

 the southern borders of the Atlantic flora. 



Passifloeace^. — Arc equally unknown to the Eocky Mountain and 

 Pacific floras. A very few species of Passijiora are indigenous to the 

 Atlantic States, one extending as far north as Ohio. 



CucuEBiTACE^. — Are few in this country, and from the interior re- 

 gion within our proper limits they are absent. The true Echinocystis is 

 peculiar to the Atlantic States; two or three species of Merjarrluza char- 

 acterize the Pacific flora ; perennial and tuberous rooted species of Cuciir- 

 bita belong to the plains east of the Eocky Mountains {G. xierennis) and 

 through drier Texano-Arizonian regions. 



Datiscace^. — A single Datisca in California, far away from all its 

 relatives. 



CACTACEiE. — Are abundant in and characteristic of the Eocky ]\Iount- 

 ain region, and still more of the Texano-Arizonian, as of the Mexican 

 j)lateau. Two s]3ecies of Opunt'm extend along the Atlantic coast to !N^ew 

 England. Twenty-six species are enumerated in tlie Eotany of Cali- 

 fornia, but a majority of them belong to the Arizunian district. 



FicoiDE^E. — Are extremelv few and uninteresting. The e;irlv natu- 



