.348 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



Pentstemon humilis Nult. ; Gray, Proc. Am. Acad. 6 : 69 [Syn. Fl. 



2': 267; Man. R. M. 277]. 



On hills and plains, up to an altitude of 2000 m. 



Montana: Sweet Water Basin, Beaver Head Co., 1888, Tzueedy^ 

 j6a ; Bozeman, 1873, Catihv, 2ji ; Helena, 1890, Kclscy. 



Pentstemon gracilis Nutt. Gen. 2: 52 [111. Fl. 3: 153; Syn. Fl. 



2'\ 26-] ; Man. R. M. 277]. 



Dry plains, up to an altitude of 2000 m. 



Montana: Beaver Head Co., 1888, Tzveedy^yj: Lima, 1895, 

 Bydberg, 2y8o; Wisconsin Creek, 1892, H. M. Fitch; West Gal- 

 latin, 1883, Scribncr, iSS : Shinberger's Canon, 1880, Watson. 



Yellowstone Park : 1888, Dr. Chas. H. Hall; Mammoth 

 Hot Springs, 1885, Tzveedy, 864.. 



* Pentstemon Tweedyi Canby & Rose, Bot. Gaz. 15 : 66. 



A small plant about i dm. high, with linear basal-leaves and 

 -almost scapose stem with a few-flowered one-sided raceme. Dry 

 hills, at an altitude of about 2000 m. 



Montana; Beaver Head Co., 1888, Tzccedy, jj. 



» * Pentstemon aridus. 



Densely cespitose, glabrous, except the glandular-pubescent in- 

 florescence ; radical leaves linear, sometimes almost subulate or 

 narrowly oblanceolate, thick and stiff, 2-4 cm. long ; stem-leaves 

 generally opposite, about 2 Qm. long, usually linear-subulate, erect; 

 flowering stems about i dm. high ; calyx 5 mm. long, glandular- 

 pubescent, its lobes linear-lanceolate; corolla about 12 mm. long, 

 blue, tubular-funnelform, the lower lip slightly longer than the upper ; 

 sterile stamen narrowly linear and glabrous, except the slightly 

 dilated spatulate villous end ; cells of the fertile anther divaricate ; 

 pod 6-8 mm. long, broadly ovoid. 



It is of about the same size as P. Tn'ccdvi, which, however, is 

 easily distinguished from it b\' the broader thinner leaves, almost 

 leafless flowering stems, one-sided inflorescence, and more plainly 

 bilabiate corolla. P. aridus more resembles P. gracilis in the shape 

 of its smaller corolla, but the whole plant is smaller and has different 

 leaves. It mav be mistaken for P. larici/olius, which is said to 

 occur in Wyoming. 



On dry hillsides, at an altitude of 2000-2500 m. 



Montana: Spanish Basin, June 23, 1897, Rydberg & Bessey^ 

 4g20 (type); Cedar Mountain, July 16, ^gji ; Beaver Head Co., 



