4 PROCEEDINGS OF THE AMERICAN ACADEMY. 



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Subgenus Eutridax. Scales of the involucre 2 - several-seriate : 

 achenes densely silky-villous or hirsute : pappus scales terminating in 

 plumose awns. 



§ 1. Scales of the involucre very unequal, regularly imbricated in 

 several to many series, gradually decreasing in size ; the outermost very 

 short, mostly scarious and rounded at the summit, very rarely somewhat 

 herbaceous or (in T. angustlfoUa) subacute, 



* Heads discoid : pappus shorter than the achenes. 



1. T. brachylepis, Hemsl. "Annual, erect," witli " slender gla- 

 brescent brauchlets" and "thickish ovate-lanceolate dentate or sometimes 

 obscurely lobed leaves." — Biol, Cent.-Am. Bot, ii, 207. — Cordillera of 

 Oaxaca, altitude 7,000 feet, Galeotti. The only specimen, seen by the 

 writers, closely approximating in its characters Mr. Hemsley's descrip- 

 tion is no. 1423 of E. W. Nelson, collected in the Valley of Oaxaca, 

 altitude 5,500 to 7,500 feet, 20 September, 1894. But although only the 

 upper portion of the root is at hand it is not unlikely perennial. 



2. T. tuberosa. Distinctly perennial ; the elongated woody root 

 at places tuberous-thickened : stem decumbent, subsimple, 3 feet in 

 height, leafy to the middle,. hirsute : leaves hirsute upon both surfaces, 

 3-nerved, 2 inches long, nearly half as broad, cuneate at the base and 

 3-cleft with sharply toothed acute lobes : heads about 6, nearly 7 lines 

 long and 6 lines in diameter : pappus only a third to half the length of 

 the achene. — Collected by C. G. Pringle, on the Sierra de San Felipe, 

 Oaxaca, altitude 7,000 to 8,500 feet, 17 November, 1894, no. 5644 a. 



3. T. Pringlei. Perennial, decumbent, much branched from near 

 the base, 2 feet high, pubescent throughout but less hirsute than the 

 preceding: root woody, tuberous-thickened at intervals: leaves lanceo- 

 late, dentate or subentire, obtusish, 1 to H inches long, scarcely a third 

 as broad, 1 -nerved: heads 2 to 4, very similar in all respects to those of 

 the preceding. — Collected by C. G. Pringle, on the Sierra de San 

 Felipe, Oaxaca, altitude 7,500 feet, 7 September, 1894, no. 5644. In 

 technical characters very close to the preceding species, but with markedly . 

 different foliage, 



* * Heads radiate : ligules evident, 



■I- Mexican species. 



++ Eays 3'ellow. 



= Pappus very short or none. 



4. T. trilobata, Hemsl. 1. c, 208, Erect much branched glandidar- 

 pubescent annual, a foot or two high, with lance-oblong obtusish and 

 coarsely few-toothed or laciniate leaves (cuneate at the base) and numer- 



