460 BOTANICAL GEOGRAPHY. 



talis, and Rhus glabriim, predominate on the open prairie, which in May and 

 June is rendered moist by the atmospheric precipitations : the vegetation, 

 nevertheless, scarcely lasts longer than these short weeks of spring. The 

 following forms may be mentioned as characteristic of the flora of the prairie; 

 they are subdivided according to their localities, although the author has not 

 arranged them in the form of a summary : Of the Leguminosae, Astragalus, 

 e. g. A. adsurgens and caryocarpm, Oxytropis, Phaca, Petalostemon, Psoralea, 

 Glycyrrhiza, and Schrankia', Malvaceae, Sida coccinea ; Cactacese, Mamil- 

 laria simplex and Opuntia missurica ; Onagrarise, (Enothera and Gaura ; 

 Synantheracese, principally Helianthese, e. g. Echinacea, Rudbeckia, Heliopsis; 

 moreover, Artemisia, e. g. A. caudata, and Lygodesmia ; Scrophulariacea3, 

 Pentstemon and Castilleja; Hydrophyllacese, Ellisia ; Boragineae, Batschia; 

 Nyctaginese, Calymenia ; Liliacese, Yucca ; Graminaceae, e. g. Sesleria dac- 

 tyloides, Crypsis, Stipa, Agrostis, Eriocoma, &c. 



The remaining large district is denominated by Geyer the upper saline 

 desert region, the area of which extends far inwards symmetrically, on both 

 sides of the Rocky Mountains, from Missouri to Lower Oregon, a desert 

 elevated surface resting upon sandy rocks, and gradually ascending from 

 1200' to more than 4000'; so that the chains of the Rocky Mountains, in 

 spite of their elevated central ridges, cannot by any means be regarded as 

 forming a boundary of vegetation. The boundaries of this immense steppe, 

 which everywhere affords pasture, Geyer considers as formed, in the north, by 

 the Saskatchawan and Lake Winnipeg ; in the east (the same as the Prince 

 of Wied), by a line running longitudinally through loway, or the former dis- 

 trict of the Sioux (Great Sioux river and Moine's river) ; in the south, by the 

 Upper Arkansas ; in the west, by the mouth of the Wallawalla, in the Oregon 

 district (more distinctly by Eremont, the union of the two principal forks of 

 this river, the Lewis river and the Upper Columbia) ; hence about 3S-54 N. 

 lat. and 77-101 W. long, from Ferro. With the exception of the pine 

 and snow -clad central chain of the Rocky Mountains, this space contains no 

 forests. The prevailing character of the flora is generally the same as that 

 described by the Prince of Wied, that of the Upper Missouri. Beyond 

 the Rocky Mountains also, as in the district of the source of the River 

 Platte, the steppe is covered with two social shrubby Artemisias (Art. triden- 

 tata and cana). The Pulpy -thorn, Sarcobatus vermicularis (S. Maximiliani 

 N.), also called the Salt-cedar, is found everywhere on the saline soil as low 

 down as Oregon ; it is a shrub, with numerous stems from 3'-8' in height, 

 with diverging thorny branches and dark-green succulent leaves. Considering 

 the similarity of the climate and soil of the prairies and the Russian steppes, 

 it is an interesting fact, that this genus, which was first recognised as distinct, 

 from the examination of Wied's collections, according to both Lindley and 

 Torrey (Fremontia ej., Satis vermicularis, Hook.), is a true member of the 

 Chenopodiacea3 (Lond. Journ. of Bot., 1845, pp. 1 and 481), and grows in 



