OF ARTS AND SCIENCES. 39 



partitis summisve integriusculis ; involucro gradatim imbricato 3-4- 

 seriali, bracteis subherbaceis oblongis obtusissimis adpressis, exterioribus 

 cinereo-puberulis ; ligulis albis deuium roseis dilatatis fere integerrimia 

 (sine lobulis internis) ; coi^ollis disci viridescenti-flavis ; pappi paleis 

 linearibua fimbriato-plumosis tubo corolla? vix adaequantihus achenio 

 dimidio brevioribus. — On rocky bluffs at Alvarez, thirty miles south- 

 east of San Luis, at the elevation of 8,000 feet. No. 489 with broader 

 leaves, 490 and 482 i with narrow leaves. A handsome species ; the 

 naked flowering branches somewhat paniculate ; heads half an inch 

 high, and the few but large and showy ligules half an inch long on a 

 rather slender tube, their width at the almost truncate apex nearly 

 equalling the length. 



Tridax (Ptilostephium) trifida, var. alboradiata. Radio 

 albo ; foliis latioribus 3-5-fidis, lobis nunc laciniatis. — Gravelly 

 slopes near San Luis, July, August. No. 511. This species includes 

 Ptilostephium coronopifolium as well as P. trijidum of DeCandolle's 

 Prodromus, not P. coronopifolium, HBK., which, as the figure shows, 

 has the pappus of plumose arista? in the manner of T. procumbens. 

 No. 508 of the present collection is, without much doubt, the true 

 T. coronopifolia ; but its ray-flowers are properly ligulate and female. 

 Nearly related to it is T. balbisioides {Ptilostephium, Spreng., Galin- 

 soga, HBK., Soyalgina, Cass.), if we may rightly refer Parry and 

 Palmer's No. 509 to that species ; but the ligule in the specimen is 

 three-cleft instead of entire and reniform. 



Tridax candidissima. Tomento albo undique lanata; ramis 

 brevibus adsurgentibus crebre foliatis pedunculo nudo scapiformi 

 superatis ; foliis linearibus (teretibus ?) obtusis sessilibus ; capitulo (an 

 semper?) homogamo ; involucro sat imbricato ; pappo modo T. pro- 

 cumbentis plumoso, aristis majoribus corollis flavis parum brevioribus. — 

 On loose ashy soil near Angostura, one hundred miles east of San 

 Luis, coll. by Dr. Palmer, March, 1879. No. 510. 



EUTETRAS, Nov. Gen. Helenioidearum. 



Capitulum heterogamum, radiatum, multifiorum ; floribus radii 

 9-12 focmineis. Involucrum campanulatum, biseriale ; bracteis requa- 

 libus disci brevioribus, exterioribus (circa 10) subherbaceis lineari- 

 oblongis substriatis, interioribus siccioribus, omnibus fere planis. 

 Receptaculum convexum, nudum. Ligula? breviusculoc, oblongie, apice 

 tridentata? ; corolla? disci ultra tubum proprium brevem angustum 

 cylindraceae, apice 4-dentatae. Anthera? 4, basi sagittatae, apice appen- 



