﻿174 Vail: Studies in the Asclepiadaceae 



The following key, perhaps, will be a help in recognizing the 

 species as I now understand them : 



Key to tlie Specie*. 



§ Follicles erect on erect fruiting pedicels. 

 Flowers greenish and white, or in no. i sometimes tinged with purple on the outside. 

 Hoods not exceeding the anthers. 



Leaves verticillate in whorls of 2-4*5, narrowly linear ; rootstock short, cov- 

 ered with fibrous rootlets. I. A. verticillata. 



Leaves very crowded, whorled or scattered, filiform, 2-3 cm. long ; stems 

 tufted from a woody rootstock. 2. A. pit mi la. 



Leaves approximated in whorls of 3-6' s, not crowded, linear, 4-10 cm. long ; 



stems solitary or tufted from a long horizontal rootstock. 



3. A. galioides. 



Leaves approximated in whorls of 3-4' s, narrowly linear, 4-10 cm. long, close 



and crow T ded at the base, elongated and often opposite above. 



4. A, subvert* cillata. 



Leaves opposite, linear, 4-8 cm. long ; margins slightly revolute : umbels 



lateral, small. 



5. A, linearis. 



Hoods exceeding the anthers ; leaves opposite, linear, 7-14 cm. long ; umbels few, 



corymbosely terminal. 



6. A. linifolia. 



Flowers ash-colored or the hoods whitish ; leaves lanceolate or linear-lanceolate, spread- 

 ing or falcate- reflexed, 6-12 cm. long, with ascending veins. 7. A. Mexicana. 



I. ASCLEPIAS VERTICILLATA L. Sp. PI. 217. 1753- 



This species was based on w Asckpias foliis vert kill at is linc- 

 ari-setaceis u Gronovius, Virg. 26. 1739, which in its turn 

 was founded on " Apocymtm Mariannm erectum Linariae an- 

 gustissimus foliis iimbellatum — Apocyno recto nan ramoso. Ro- 

 rismarini foliis umbellis flornm candidis V Plunkenet, Mantissa, 



*7- &* 336- I7°0- The figure is a very good one, and there is no 

 doubt as to what plant was intended. It is the species common 

 on our eastern seaboard and western praires ; but probably not 

 what passes as Asckpias verticillata in Mexico nor the forms 

 known as A. verticillata var. sabverticillata in the Southwestern 

 States.* 



vicinity 



stant in the following important characters : 



untry 



Asdepias Simpsoni Chapm. Fl. ed. 3, 346. 1897, a low pine barren species 

 from South Florida, is nearly related to A. verticellata, but I have not seen authentic 

 specimens of it. 



