BOTANICAL INFORMATION. 25 



coke-like surface : the same mineral appears on the Sweet- 

 water River and Soda-springs, and nearly the same in 

 the shape of extensive dykes, in the Black Hills and other 

 eastern ranges of the Rocky Mountains. 



Again, the same species of rock assumes in some localities 

 a somewhat obsolete columnar form, when it is less heavy, 

 and not so distinctly crystallized, walling sides of plateaux, 

 1000 — 2000 feet in height above the wide valleys, but only 

 around their base ; higher up, the same claystone or clayey 

 sandstone appears again, with a slight southerly inclination 

 and confused surface. These stony table-lands are the habitat 

 of Stanleya viridiflora, Sida dissecta, Mammillaria,* Castilleja 



* This Mammillaria is one of the largest in size among the Conothelte, 

 and like another species of the same division from the sandy plains at the 

 uppermost forks of the Platte, always solitary and with yellowish-white 

 spines. Both species were lost, I regret to say, but I hope that future 

 travellers will again find them. The first I noticed in my journal as 

 M. applanata, having somewhat the form of M. depressa, and very small 

 lurid-reddish flowers. The one from the Platte-plains is small in size, 

 somewhat pear-shaped, with very dense and closely radiating spines, which 

 cross each other ; the flowers likewise small, rose-coloured. It was first 

 discovered by Dr. Mersh, of Luxemburgh, in the suite of Sir Wm. Stewart ; 

 so I noted it down in my journal, as M. Mershii. A third species of Mam* 

 miliaria I found on the Oregon plains, while searching for a Melocactus. 

 Of this I brought dry specimens to London, and Mr. Scheer, at Kew, has 

 already raised several from seeds. The above mentioned Melocactus was 

 gathered by Chief- factor Macdonald, at Fort Colville, but the exact habitat 

 was forgotten ; the one specimen found was afterwards in possession of 

 Dr. Tolmie on the lower Columbia. From the information I could gather 

 at Fort Walla- Walla, the true habitat of this Cactus is at the " Priests' 

 Rapid," on a rocky island in the Columbia River, about sixty miles above 

 Fort Walla- Waila. I received the intelligence too lale, but hope that by 

 publishing it, other botanists may have the opportunity of getting the 

 plant without loss of time. 



A circumstance seems to me to deserve some notice respecting the above 

 three Mammillarice ; they become buried by sand and dust at the approach 

 of winter, so as to be hardly visible ; even in the summer months they 

 scarcely show more than one-third above ground. This seems, indeed, 

 a provision of nature to protect these tender succulents against the in- 

 tense cold of so high a latitude and altitude. Such is not the case with 



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