[ 174 ] 84 



The route along the North fork of the Platte afforded some of the best plants in the collection. 

 The senecio rapi folia, Nutt., occurred in many places, quite to the Sweet Water ; lippia (zapania) 

 cuneifolia (Torr. in James's plants, only known before from Dr. James's collection :) cercocarpus par- 

 vifolius, Nutt. ; eriogonum parvifulium, and coespitosum, Nutt.; shepherdia argentea, Nutt., 

 and geran turn Fremontii, a new species, (near the Red Buttes,) were found in this part of the 

 journey. In saline soils, on the Upper Platte, near the mouth of the Sweet Water, were collected 

 several interesting Cheuopodiaceje, one of which was first discovered by Dr. James, in Long's 

 expedition ; and although it was considered as a new genus, I did not describe it, owing to the want 

 of the ripe fruit. It is the plant doubtfully referred by Hooker, in his Flora Boreali Americana, 

 to Batis. He had seen the male flowers only. As it is certainly a new genus, I have dedicated it 

 to the excellent commander of the expedition, as a well-merited compliment for the services he has 

 rendered North American botany. 



The Sweet Water valley is a sandy plain, about one hundred and twenty miles long, and gen- 

 erally about five miles broad ; bounded by ranges of granitic mountains, between which the valley 

 formation consists, near the Devil's gate, of a grayish micaceous sandstone, with marl and white 

 clay. At the encampment of August 5th- 6th, there occurred a fine white argillaceous sandstone, 

 a coarse sandstone or pudding-stone, and a white calcareous sandstone. A few miles to the west 

 of that position, Lieutenant Fremont reached a point where the sandstone rested immediately upon 

 the granite, which, thenceforward, along his line of roufp, alternated with a compact mica slate. 



Along the Sweet Water, many interesting plants were collected, as may be seen by an examina- 

 tion of the catalogue ; I would, however, mention the curious Oenothera Nuttallii, Torr. and Gr. ; 

 eurotia ianata, Mocq. ; (Diotis lanata, Pursh.,) which seems to be distinct from E. ceratoides ; 

 thermopsis montanu, Nutt. ; gilia pulche/la, Dough ; senecio spartioides, Torr. and Gr. ; a new 

 species, and four or five species of wild currants, (vibes irriguum, Dougb, &c. ) Near the mouth 

 of the Sweet Water was found the plant ago eriophora, Torr., a species first described in my Dr. 

 James's Rocky Mountain Plants. On the upper part, and near the dividing ridge, were collected 

 several species of castilleja ,■ penlstemon micrantha, Nutt: several gentians ,■ the pretty little 

 androsacc occidentals, Nutt. ; solidago incana, Torr. and Gr. ; and two species of eriogonum, 

 one of wliich was new. 



On the 8th of August, the exploring party crossed the dividing ridge or pass, and found the soil 

 of the plains at the foot of the mountains, on the western side, to be sandy. From Laramie's fork 

 to this point, different species of artemisia were the prevailing and characteristic plants ; occupying 

 the place of the grasses, and filling the air with the odor of camphor and turpentine. Along Little 

 Sandy, a tributary of the Colorado of the West, were collected a new species of pkuca (P. digi- 

 tata,) and parnassia jimlriata. 



On the morning of the 10th of August, they entered the defiles of the Wind river mountains, a 

 spur of the Rocky mountains, or northern Andes, and among which they spent about eight days. 

 On the borders of a lake, embosomed in one of the defiles, wire collected sedum rhodiola, DC., 

 (which had been found before, south of Kotzebue's sound, only by Dr. James :) senecio hydrophi- 

 lus, Nutt. ; Vaccinium uliginosum ; behtla glandulosa, and B. ucddentalis, Hook. ; eleagnus 

 argentea, and shepherdia Canadensis. Spine of the higher peaks of the Wind river mountains 

 rise one thousand feet above the limits of peiSktual snow. /{Lieutenant Fremont, attended by four 

 of his men, ascended one of the loftiest peaks aBthe 15th of August- On this he found the snow 

 line twelve thousand five hundred feet above the lerel of the stfa. The vegetation of the mountains 

 is truly alpine, embracing a considerable number of species 'Jffommon to both hemispheres, as well 

 as some that are peculiar to North America. Of the' formae Lieutenant Fremont collected pleura 

 alpinum ; oxyriareniformis; Veronica alpina ,• several species of salix,- carex atrata ; C.panicea,- 

 and, immediately below the line of perpetual congelation, silene acaulh, and polemonium cceruleum, 

 /? Hook. Among the alpine plants peculiar to the western hemisphere, there were found oreophila 

 rnyriij-Iia, Nutt. ; aquibgia coerulea, Torr. ; pedicularis sirrecla, .Jenth. ; pulmonaria ciliata t 

 James; silene Drttr&tnondii, Hook. ; menzicsia empetriformis, poientilla gi acilis, Dougl. ; ser- 



