I IO 



FIELD COLUMBIAN MUSEUM BOTANY, VOL. III. 



illary loose cymose corymbs! branchlets and pedicels 'slender, some- 

 what flexuous, tomentulose: heads 3 to 4 mm. in diameter, 4 mm. high, 

 4-4.5 mm. broad; rays 5, disk flowers 10 to 15: involucral scales about 

 2-seriate, in 3-4 series of 5 each, ob- 

 tuse, the outer shorter, puberulent, 

 tomentose at the summit: rays I 

 mm. to 1.5 mm. long, subrotund, bid- 

 entate: disk flowers narrowly cam- 

 panulate, glandular dotted at the 

 apex: receptacle conic; scales 

 broad, emarginate, fimbriate, the 

 summit clothed with thickened 

 hairs: pappus of 3, rarely 2 slender, 

 inconspicuous, divergent, cartilagin- 

 ous awns, .25-.3 mm. long, the lat- 

 eral pair slender entire, the ventral 

 one broadened, tridentate : mature 

 achenes black, oblong cuneate or nar- 

 rowly obovate, 2 mm. long, 1.2-1.3x2.4 mm.; in section flattened 

 triangular in outline, the dorsum convex, the ventral angle rounded 

 and facets concave; puberulent, clothed with brownish white thickened 

 hairs, more dense at the summit and on the ventral angle. 



Collected by Dr. Arthur Schott, Labcah, Yucatan, July jo, 1865, No. 

 264; and by Dr. G. F, Gaumer at Merida and at Progreso, Yucatan, No. 

 1166. 



Hab. Labcah, July 30, 1865, Schott 264; "shrub 3 feet high, 

 abundant at Progreso" Gaumer n66(type), Calotmul 2213. 



Called SANTA MARIA in Yucatec and CHALCHA (see Pluchea 

 odorata) by the Mayas. 



Perhaps most nearly related to P. fruticosum Less., which, however, 

 has somewhat broader leaves, much less attenuate at the base, and more 

 hirsute above. P. Schottii is further distinguished by the looser 



corymbs, 3-4 seriate involucre, more 

 conspicuous rays, longer achenes, 

 and divergent awns, 3 in number. 



Parthenium fruticosum Less. Lin- 



naea, 5:152. 



Shrubby stems and branches 

 with pale cortex, terete, striate, sub- 

 tomentose ; leaves alternate, short 

 wing-petioled, triangular to cordate, 

 acute, dentate, scabrous above, vil- 

 lose-pubescent below. Inflorescence 

 a terminal, dense, flat-topped or 

 rounded, cymose corymb; branchlets 

 and pedicels, stout, rigid, tomentose. 



Heads 4 mm. high, 5-6 mm. broad; rays 5-6, disk flowers numerous. 

 Involucral bracts in 2 series of 5-6 each, the inner much longer; outer 

 ovate, rounded and ciliate at the summit, pubescent; inner orbicular, 



