﻿Vail: Studies in the Asclepiadaceae. 37 



prolongation of the thickened crest-like midrib and much shorter 

 than the erect, obtuse lateral ones, at the base concave and gib- 

 bous, each inner margin spreading into an erosely truncate lobe 

 which usually overlaps that of the next hood and terminates in an 

 interior ring of five 2-lobed minute processes or appendages be- 

 tween the anthers ; anther-wings salient and conspicuously auricu- 

 lately notched slightly below the middle, narrowed at the base ; 

 follicles slender-fusiform, straight, erect on erect fruiting pedicels, 

 about 8 cm. long, 6-7 mm. wide, acute, minutely pubescent ; seeds 

 about 5 mm. long, thin ; coma 3 cm. long. {Nothaccrates A. Gray.) 



Ka 



Texas. J 



Illustration : 



/• 



Nebraska: Thomas Co., Rydberg, no. 1420. Kansas: Ar- 

 kansas River, Fremont, 1845 ; Fort Riley, E. E. Gayle, no. 518 ; 

 \V. E. Rusby, 1878; Manhattan, M. A. Carleton ; Manhattan, 

 Norton, 1892. "Arkansas :" Nuttall, in Herb. Columbia Univer- 

 sity. 



7. ACERATES RUSBYI Sp. nOV. 



Glabrous up to the inflorescence, glaucous. Stems erect, 

 stout, solitary ? 6-8 dm. high or more, from a slender, branched 

 rootstock ; leaves linear to filiform-linear, 8-17 cm. long, 2-5 mm. 

 wide, sessile, acute at the apex, rather distant, approximated in 

 whorls of 3 above, scattered-alternate and sometimes in th 

 below ; peduncles 1—3.5 cm - lon R I umbels many-flowered, lateral, 

 •solitary or in pairs; pedicels about 1 cm. long and with the nu- 

 merous involucral bracts minutely puberulent; corolla-segments 

 4-5 mm. long, dull purple on the outside, greenish on the inner 

 surface ; column short but distinct ; hoods erect, yellowish, with 

 a darker or purplish? midrib or keel, shorter than the anthers, 

 •concave, truncate at the apex, auricled below the middle at the 

 slightly infolded ventral margin ; horn very slender, weak, trans- 

 parent, arising from the base of the keel of the hood and but rarely 

 reaching its apex ; anther-wings salient and notched near the base. 

 Follicles not seen. 



With the general appearance of A. anriculata, but very easy 

 to distinguish by the more regular disposition of the leaves, the 

 shorter hoods and the obscure horns, which appear merely as a 

 detached and free midvein or keel. Oak Creek, Arizona, June 

 23, 1883, collected by H. H. Rusby and distributed as Acerates 

 anriculata Engelm. ; Williams, Arizona, collected by Tourney, no. 



249. June 28, 1892 (in U. S. Nat. Herb.). 



