ROBINSON AND GREENMAN. — GENUS TRIDAX. 9 



Galeotti, no. 2472. A species not seen by the writers. The description 

 is translated and condensed from the original characterization. 



-1- -t- Leaves very narrow, linear or lance-linear, or deeply cleft into narrow di- 

 visions : heads rather small, 4 to 6 lines broad : rays small, bilabiate, the 

 external lip tritid. 



1 7. T. coronopifolia, Hemsl. Low, much branched and spreading, 

 pubescent or hirsute ; leaves lance-linear, denticulate, lacinately toothed 

 or piunatifid with narrow linear unequal acute segments : peduncles 

 slender, toward the summit finely strigillose with appressed white hairs, 

 and lacking the glandular-tipped hairs so common in the genus : rays 

 yellow (or white) : pappus scales uuequal, some of them subulate and 

 ciliated, others plumose with scarcely dilated base. — Biol. Cent.- Am. 

 Bot. ii. 207. Ptilostephmm coronopifoUum, HBK. Nov. Gen. & Spec, 

 iv. 255, t. 387. We have little hesitation in including in this species 

 also Tridax trijida, Gray, Proc. Am. Acad. xv. 39 {Ptilostephium tri- 

 fidum, HBK. 1. c. 255, t. 388), notwithstanding the considerable differ- 

 ence in the pappus represented by Kunth. After the examination of a 

 number of specimens we doubt the specific significance of the difference in 

 length of the pappus, and as to the difference in the breadth of the scales 

 that is often considerable upon the same achene. — Mexico without lo- 

 cality, 7%. Coulter, nos. 348, 430, and Berlandier ; State of Mexico, 

 Bilimek, no. 491, also Bourgemi, nos. 164, 705 ; Tacubaya, Schaffner ; 

 Mt. Orizaba, altitude 9,000 feet, Seaton, no. 273 ; Oaxaca, Soledad de 

 Etla, altitude 5,300 feet, L. C. Smith, no. 361, and by same collector at 

 Telixtlahuaca, no. 866 ; also by E. W. Nelson, in Valley of Oaxaca, 

 altitude 5,100 to 5,800 feet, no. 1229. The formal variety alboradiata 

 {T. trijida, var. alboradiata, Gray, Proc. Am. Acad. xv. 39), with white 

 rays, but apparently without other significant or constant differences, has 

 a somewhat more northerly distribution, having been collected at San 

 Luis Potosi, Schaffner, no. 239, Parry 8^ Palmer, no. 511 ; in Jalisco, 

 Pringle, no. 2902 ; and in Guanajuato, Duges, no. 438. 



18. T. lanceolata, Klatt. "Lower leaves broadly lanceolate and 

 upper lance-linear, entire : chaff obovate." — Leopoldina, xxiii. 6. — 

 '• Tehuacan, Liebmann, no. 205; Cuernavaca, Berlandier, no. 1063." A 

 species not seen by the writers and (as to description) distinguished from 

 the preceding species chiefly by the characters quoted. 



19. T. imbricata, Schz. Bip. "Leaves linear-lanceolate, entire, 

 or 1-3-toothed, pilose, ciliated on the margins : external scales of the 

 involucre obtuse, striate, dorsally puberulent." — Schz. Bip. in Klatt, 

 Flora, 1885, 202. — " Real del IMonte, Ehrenberg, no. 355." We suspect 

 this to be merely a form of T. coronopifolia. 



