294 PROCEEDINGS OF THE AMERICAN ACADEMY 



§ 3. SetispincB : adscendentes : articuli plerumque minores : aculei 

 pauci, teretes seu vix angulati, graciles, flexiles, pallidi : bacca 

 minor. 



13. O. TENUisPiNA, E. in B. C. R. : articulis majusculis obovatis 

 basi attenuatis Isete viridibus ; pulvillis subapproximatis setas graciles 

 breves fulvas gerentibus plerisque armatis ; aculeis 1-2 elongatis 

 al bid is cum 1 -4 brevioribus inferioribus ; floris flavi ovario clavato ; 

 petalis obovatis retusis ; bacca oblonga profunde umbilicata ; semini- 

 bus minoribus. 



Sand-hills near El Paso : fl. May. — Joints 3-6 inches long, 2-4 

 wide ; leaves very slender, hardly 2 lines long ; upper spines sub- 

 erect, or spreading, 1^ - 2J- inches long ; flower 22- - 3 inches in diam- 

 eter ; seeds less than 2 lines in diameter, very irregular. — Similar 

 in many respects to 0. phceacantha, which grows with it ; but readily 

 distinguished by the spines and fruit. 



14. O. SETISPINA, E. in Salm, H. D. : articulis suborbiculatis par- 

 vis glaucis ; pulvillis confertis setas flavidas gerentibus, omnibus arma- 

 tis ; aculeis 1-3 longioribus subangulatis et 3-7 brevioribus plus 

 minus deflexis, omnibus gracillimis. 



Pine woods in the mountains west of Chihuahua, Dr. Wislizenus. 

 Joints not over 2 inches long; pulvilli only 3-4 lines apart ; longer 

 spines 1 - Ig- inches long, very slender, like bristles. Flower and 

 fruit unknown. 



15. O. FiLiPENDtJLA, E. in B. C. R. : glauca ; radicibus nodoso- 

 incrassatis ; articulis minoribus orbiculatis seu obovatis seu oblance- 

 olatis tenuibus ; pulvillis approximatis setas virescenti-flavas graciles 

 numerosas gerentibus armatis vel inermibus ; aculeis, si adsunt, 1-2 

 elongatis subangulatis cum 1-2 minoribus, omnibus albidis ; floris 

 purpurascentis ovario gracili ; stigmatibus 5 ; seminibus minoribus 

 tumid is. . 



Alluvial bottoms of the Rio Grande near El Paso, and eastwai'd on 

 the Pecos : fl. May and June. — The long knotted roots, the small 

 bluish joints, with the very small leaves and very long bristles, to- 

 gether with the purple flower, and thick very narrowly margined 

 seeds, distinguish this species from all others. Plant 6-12 inches 

 high, joints Ig- - 3 inches long, 1-2 wide ; pulvilli 4-6 lines apart ; 

 lower spines 1-2 inches long. Flower 2^ inches in diameter. Seed 

 hardly 2 lines in diameter. 



