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36 Vail: Studies in the Asclepiadaceae. 



■ 



and often twisted with age ; peduncles 5 mm.-2 cm. long, and with 

 the 1 cm. long, slender pedicels and numerous slender involucral 

 bracts, minutely puberulent ; umbels many-flowered, lateral, 1 or 2 r 

 sometimes 16 on the same stem; column very short; calyx-seg- 

 ments minutely puberulent; corolla-segments greenish, tinged with 

 dull purple on the outside, about 4 mm. long ; hoods yellowish, with 

 often a purplish keel, erect, crenately truncate or emarginate at the 

 apex, the involute sides spreading at the base into broad, obscurely 

 crenate auricles ; anther-mass globose, anthers narrow and of equal 

 width, entire or possibly notched and twisted at the middle, in- ^ 

 curved over the anthers at the summit, the intermediate spaces 

 marked by a verticle dark purple line; follicles erect on reflexed 

 fruiting pedicels, about 8 cm. long, obliquely fusiform, acute, 

 glabrous ; seeds 6 mm. long, very thin ; coma 2 cm. long. 



Rocky ground and prairies, Nebraska, Kansas and Colorado- 

 to New Mexico and southern Texas. June to September. 



Nebraska: Banner Co., Rydberg, no. 230. Kansas: Dodge 

 City, Smyth, no. 164, and Caldwell, no. 273; " Kansas River,"' 

 Fremont, 1845. New Mexico : Wright, no. 1687; Copper Mines,. 

 Mex. Bound. Surv., Bigelow ; White Mts., Norton, 1895. Texas: 

 Kerrville, Kerr Co., Heller, no. 1868 (distributed as Acerates 

 stenophylla). 



Illustration: Britt. & Brown, 111. Fl. 3: / 2924. 1898. Ined. 



6. Acerates angustifolia (Nutt.) Decne. ; DC. Prodr. 8 : 522. 



1844. 



Polyotus cuigustifoliusV>w\X. Trans. Am. Phil. Soc, Ser. 2, 5 : 201. 



1834 



Asclepias stenopJiylla A 

 Asclepias auriailata He 



In part. 



1876. 

 1892. 



Stems mostly several from the same stout tuberous root-stock, 

 erect, straight. 3-6 dm. high, clothed with a minute, mostly re- 

 trorse puberulence, becoming glabrate below; leaves alternate, 

 scattered or some of the lower ones opposite, sessile, narrowly 

 linear, 5-12 cm. long or more, glabrous, the revolute margins and 

 thick midrib scabrous beneath; umbels small, 10- 15 -flowered, 

 short-peduncled or subsessile, lateral, 7-13 or more on the 

 same stem ; pedicels 7-10 mm. long, minutely spreading or re- 

 trorse-pubescent; corolla-segments 5 mm. long, oblong, obtuse or 

 acutish, greenish; hoods white, attached over the whole of the 

 short column, erect, as high as the short anthers, laterally corn- 



mere 



