GRAY WD HOOkT.i: <>\ THE ROCfcY MOl NTAIN FLORA. 37 



(tillti hardly crosses the Uleghanies; the single Liquidambar is equally 

 of eastern range, thougn it extends into and throngh Mexico. 



1 1 ai.mi: \«.i: i:. — Arc of small account. The amphigssan HippurU and 

 one or two of ftfyrtopayMuro extend across the continent northward; bnt 



- rpiiHtcn, of two species, is restricted to the Atlantic llora. 



RfELASTOMACEiE. — Rhexia of t lie Atlantic ilora alone represents this 

 great typical order in a temperate climate. 



\a Tin: ut..k. — Largely tropical or subtropical ; two or three species of 

 J. mmannia and Lythrttm are of wide distribution; and the Atlantic States 

 have a Cuphea and a Kestm, Eastern South American types. The pecu- 

 liar genus Dtdiplu is nearly an aquatic Ammannia. 



OlTAORACEJE. — A largely American order. WpildbiUtil, a cosmopoli- 

 tan genus, is most diversified in the Pacific flora. Clarl-ia, Boisduvalia, 

 Euhbu8, Eucharidium,anj\ Heterogaura are restricted to it; Zauschneria, 

 Qayophytum, and the principal wealth of the great genus Oenothera, to 

 the Rocky Mountain and Pacific region ; Qwnra and Stenosiphon mainly 

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

 a and the diurnal yellow- flowered Oenothera 1 , with elavate capsules, 

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

 genera, but also Chilian. 



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

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

 butwell represented in the Rocky Mountain and Pacific floras by various 

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

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

 and the Rocky Mountains. Eucnide and Petalonyx are Texano-ArizO- 

 nian genera. 



i:j:. — Tropical plants; one or two species of Turnera ou 

 the southern borders of the Atlantic flora. 



P \ssu 'i.niiAc!;.!:. — Are equally unknown to the Rocky Mountain and 

 He floras. A very few species of Passiflara are indigenous to the 

 Atlantic States, one extending as far north as Ohio. 



( ! < ruRBi i agejb. — Are few in this country, and from the interioi re- 

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

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

 acterize the Pacific ilora : perennial and tuberous rooted species of Cueur- 

 _ bo the plains east of the Rocky Mountains (C. perenn is) and 

 through drieT Texano-Arizonian regions. 



1>\ji-< \< i i . — a single Datisca in California, faraway from ail its 

 relati 



—Are abundant in and characteristic of the Rockj Mount- 



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



plateau. Twospeciesol Opuntia extend along the Atlantic coast to New 



species are enumerated in the Botany of Oali- 



P rnia, bul a majority of them belong to the Arizonian district. 



luiiiiu;.;.. — .\: iraely few and uninteresting. The earlj n 



