W9.1.] GRAI AND HOOKEB OH nil. ROCKY MOUNTAIN FLORA. 17 



morphous ami of immense geographical range, it is worth Doting here 

 rliat the other genus, Littorella, till now supposed to be * holly European, 

 has been detected at three or four stations within and near the northern 

 borders of the United state-. 



\'\ <-i AiiiN \ci: i:.— Air essentially absenl from the Atlantic flora, 



abundant in the Texano-Arizonian : arc represented by Oxybaphus <m 

 ihe plains east of the Rocky Mountains and by Abronia beyond them; 

 also by QuamocUdion or Mirabilis with several-flowered calciform invo- 

 lucre. The Great Basin lias a peculiar genns, Hermidium of s. Wat- 

 son, allied to Bougainvilkea of South America, but herbaceous. 



An lb \MAcr..i: weeds excluded).— Are chiefly of the Rocky Mount- 

 ain region in its wanner and drier parts. Aenida, however, is more 

 eastern. 



ChenOPODIACEJB. — Are Of similar distribution, but far more numer- 

 ous and diverse. They are the most characteristic and abundant of the 

 plants of the dry interior region, as has been elsewhere stated, and 

 they naturally extend into the Pacific flora more than into the Atlantic. 

 Atriplex is the great genns. Grayia and Sarcobatus are the endemic 

 shrubby genera. Spirostackys is of an extratropical South American 

 type. Cijclohnnn and Suckleya are herbs peculiar to the eastern plains. 



Piiytolaccace.e. — Are represented only in the Atlantic flora, and 

 by a single Phytolacca, Eivina belonging farther south. 



POLYGONACE.fi. — The genuine Polygoncm on the Atlantic and Pacific 

 >ides by Polygonumnml Burnt p, and by Polygonella in the southern part 

 of the former : ami there are a few in the interior, where Bumex venosns 

 characteristic plant. Bui the most characteristic plants of the two 

 western floras, ami the most numerous in species, if not in individuals, 

 11 «■ the Eriogonece. The genus Eriogonum, founded at the beginnis 

 the century npon the single-known and still the only Atlantic species, 

 comprises nearly ion species in our western floras, and the subsid- 

 iary genera [Oxytheca, Gentrostegia, Chorizanthe, Nemacaulis, Hollisteria % 

 and / -'.all mainly Galiforni an, and three of them also Chilian) 



about three score more. Pfe . of California, proves to be most 



ted to the arctic-alpine Kn ligia. Another type is represented in 

 southern part of the Atlantic flora by the peculiar genus Brunnichia. 

 Podostemaoks. — Aquatic plants of tropical or subtropical riv< 

 ly of the southern hemisphere. A single Podostemdn, on which 

 j'tiiH and order were founded., belongs to the Atlantic Unit* 

 >ners ai»- all in Brazil, Madagascar, and India ! 

 Ab :. — Absent from the whole intermediate region, 



species ol I the Atlantic and three othei 



the Pacific flora; tin »rmerandonein thel 



Piper i i us in the Atlantic flora, 



me Chino Japanese Hi M if do! a 



difornia and then< el o; its relati 



