BOTANICAL GEOGRAPHY. 459 



Geyer's reports upon the characters of the vegetation 

 of the prairies on this side of and beyond the Rocky 

 Mountains (Lond. Journ. of Bot., 1845, pp. 479-92, and 

 653-62), in connexion with Fremont's investigations 

 (vid. inf.), are immediately connected with the descrip- 

 tions given by the Prince of Wied, to which the former 

 are far inferior in regard to their too aphoristic style, 

 but are as superior in systematic botanical knowledge. 



The traveller ascended the Platte River from the State of Missouri, 

 through the Osage district, as far as its source in the Rocky Mountains, 

 traversed the mountains and the Colorado of California at about the forty- 

 second parallel, and thus arrived at the Oregon territory. The western 

 and southern limit of the prairies, which, to the south of Arkansas (accord- 

 ing to De Mofras' map), are connected with the forests of New Mexico 

 (37) are not far from the Lower Kanza, in the district of Osages 

 (39 N. lat.) Hence even here the forests of the valleys along the 

 river become more numerous, the prairies abound to a greater extent in 

 flowers, and the period of the summer drought is shortened. The most 

 common species among the deciduous trees of Illinois, which are almost 

 the same as those mentioned by the Prince of Wied (Ann. Rep. for 

 1842), and which also form the forests of the banks of the river on the 

 Lower Missouri, gradually meet here with their western boundary, and they 

 diminish in height the nearer they approach the sandy valley of the Platte. 

 The herbaceous plants of this fertile prairie, however, become proportion- 

 ately more numerous, and produce an uninterrupted succession of flowers 

 throughout the spring and entire summer. In April isolated spring plants 

 appear ; in May and June the whole of the undulating surface for an immense 

 distance is in flower, the plants consisting, e. g. of Amorpha canescens, 

 Batschia, Castilleja, Pentstemon, Cypripedium candidum, &c. ; taller herbaceous 

 plants follow: Petalostemon, Baptisia, Phlox aristata, Asclepias tuberosa, 

 Lilium canadense, and Melanthium mrginicum ; and finally, in the latter part 

 of the summer, almost exclusively Synantheraceae, from tall Helianthese 

 down to the dwarf Aster sericem. 



The rich soil of the prairies terminates at the river Platte, with the lime- 

 stone of the Missouri, which favours the vegetation detailed above. The 

 lower terrace follows next ; it is 900'-1000' in height, and further up the 

 stream is connected with the elevated surface of the upper steppe. The 

 stony and sandy crust of the earth is formed of the detritus of granite, which 

 is expanded over horizontally laminated sandstone and bituminous slate. The 

 woods on the islands of the river then consist of Popuhis canadensis, Ulmus 

 americana and/w/m, Negundo and Celtis occidentalis ; on the bank, thickets 

 of Salix long i 'folia, with Amorpha frutescens, Rosa parvi folia, Rubus occiden- 



