4(!0 Vail: Studies in the Asclepiadaceae 



those of A. syriaca in contrast to the long-peduncled terminal 

 umbels of A. ample xicaulis. The flowers are intermediate between 

 the two species, with the characteristic distinct stripe down the 

 back of the hood that appears in fresh specimens of A. amplcxi- 

 cmilis. The hoods of A. amplexicaulis vary very greatly in size, 

 and in the undulations of their apical margins. 

 New York Botanical Garden. 



Explanation of plates 16-19 



Plate 16 



la. Asclepias syriaca L. , follicle, lb. Asclepias syriaca L. , leaf. 2. Asclepias 

 intermedia Vail, leaf. 3. Asclepias amplexicaulis Smith, leaf. 4. Asclepias kansana 

 Vail, follicle. 



Figures la, lb and 3 were drawn from fresh material ; 2, from the fresh type 



specimen; 4, from specimen collected by W. A. Kellerman, 1890. All figures 2 /$ 



nat. size. 



Plate 17 



I. Asclepias syriaca L. 2. Asclepias intermedia Vail. 3. Asclepias amplexi- 

 cattlis Smith. 



Figures 1 and 3 were drawn from fresh material ; 2, from type specimen. 



In each case a, flower, X 2 - ^> calyx-segments, X about 6. c, hood, front 



view, X about 6. d, hood, side view, X about 6. e, gynostegium, X about 6. f, 



pollinia, X J 4- 



Plate 18 



Asclepias kansana Vail, a, flower, b, calyx-segments, c, hood, front view. 

 d, hood, side view, e, gynostegium. f, pollinia. g, basal leaf. //, upper stem leaf. 

 The figures were all drawn from no. 762, collected by J. B. Norton, 1896. 



Plate 19 



Asclepias Bicknellii Vail, a, flower, b, calyx-segments, c, hood, front view. 

 d, hood, side view, e, gynostegium. f, pollinia. g, basal leaf, h, stem leaf. 

 The figures were all drawn from the type specimen, when fresh. 



