﻿Vail : Studies in the Asclepiadaceae 175 



Rootstock short, covered with numerous fibrous rootlets, stems 

 angled, glabrate or minutely pubescent in lines, simple or more 

 rarely branched. Leaves opposite or whorled (in depauperate speci- 

 mens sometimes all of the upper leaves are opposite), all very slen- 

 der and revolute, though specimens are found which have plane 

 leaves. The umbels are rarely more than 2.5 cm. in diameter, and 

 are situated in alternate axils of the leaves, though occasionally 

 a specimen is seen with opposite umbels and more rarely with two 

 or three umbels together, or in some robust specimens an umbel is 

 seen for each leaf. The corolla-segments are greenish, with some- 

 times slight traces of purple on the outer surface ; hoods white, 

 with a darker keel when dry, truncate at the apex, lobed at the dis- 

 tinctly angled sides, scarcely reaching the summit of the anthers ; 

 anther-wings entire or minutely notched. The horns are much 

 exserted and often meet or overlap over the stigma. 



It occurs in dry and often sterile soil from Maine to the North- 

 west Territory, south to Florida, and Texas. It may also possibly 

 be found in Arizona, and I have seen two specimens from New 

 Mexico (Vasey, Herrick), but as yet have not seen any from 

 Mexico which I could refer to A. verticillata. The species so-called 

 which does occur there is, I am inclined to think, Asclcpias gali- 

 oidcs H.B.K. and a good species. 



In Hemsley, Biol. Centr. Am. 2 : 327, 188 1-8 2, A. verticillata 

 is listed as a Mexican specfes, but the plants enumerated in confir- 

 mation of the statement, those of Parry and Hartweg, are what 

 have been known as A. verticillata var. subvcrticillata. Hartweg's 

 plant from Leon, Mexico, is so labeled in Herb. Gray, and in 

 every particular answers the description of the plant of H.B.K. 



2. A^clepia.s pumila (A. Gray) Vail ; Britt. & Brown, 111. Fl. 3 : 



12./. 2921. 1898. Ined. 



Aschpias verticillata var. pumila A. Gray, Proc. Am. Acad. 12 : 

 71. 1876. 



This species is characterized by a ligneous base and short 

 woody rootstock apparently without the fascicled fibrous rootlets 

 of A. verticillata. The stems are lower with the same narrowly 

 linear or filiform revolute margined leaves, but commonly much 



