464 PROCEEDINGS OF THE AMERICAN ACADEMY, 
Cumaral, Colombia, André, no. 1120, to British Guiana and tropical 
Brazil, where apparently common. 
+ + Leaves narrowed to a petiole or an exauriculate base: stems solitary. 
++ Leaves rhombic to elliptic-oblong, obscurely toothed, undivided. 
30. M. rraccrpum, Benth. Vidensk. Meddel. 1852, 86. I. tenellum, 
var. flaceidum, Benth. Bot. Sulph. 115 (1844). — Nicaragua near 
Granada, Oecrsted; Costa Rica, San Francisco de Guadalupe, Tonduz, 
nos. 7187, 8498; Tepic, Mexico, Hinds, Palmer, no. 1814 (starved 
specimens). 
+ ae L li oblong and unlobed or deeply cleft into narrowly oblong 
segments. 
s 31. M. uiserpoum, HBK. Nov. Gen. & Spec. iv. 273, t. 399 (1820). 
M. coronopifolium, Sch. Bip. in Hemsl. Biol. Cent-Am. Bot. ii. 145 
(1881), without character. — Arizona, Apache Pass, and near Ft. Hua- 
chuca, Lemmon, nos. 331, 2795, Santa Rita Mountains, Pringle ; Sonora, 
Wright, no. 1205; Chihuahua, Pringle, no. 297; Durango, Palmer, no. 
A86 (coll. of 1896) ; San Luis Potosi, Parry & Palmer, no. 44433 
Jaliseo, Palmer, no. 260 (coll. of 1886), in part; Tacubaya, Bilimek, 
no. 593, Schaffner, no. 195. — Except in the nature of the pubescence 
this species closely simulates W. sericeum, Lag. 
+ + + Leaves obovate, narrowed to an exauriculate base : stems several from the 
very base. 
32. M.arvense. Prostrate spreading annual; root fibrous; stems 
“several, 1 to 2 dm. long, more or less branched, purplish, covered all 
around with short weak white hairs: leaves obovate, eutire or obso etely 
crenate, rounded at the apex, 3-nerved above the acuminate and slightly 
connate base, bright green and glabrous or nearly so upon the upper 
surface, distinctly paler and hispidulous upon the nerves beneath, 1.2 to 
2.5 cm. long, 1 to 1.6 em. broad: heads very small, surrounded by small 
ovate to orbicular foliaceous bracts and borne close in the forks of the 
stem and also upon such short lateral cymes as to appear axillary; outer 
bracts of the involucre 2, ovate, distinct at the base, obtusely pointed ¢ 
ray flowers 1 to 3, disk flowers about equally numerous: fruits semi 
obovate, strongly compressed, reticulated upon the sides, more OF Jess 
tuberculate dorsally. — Collected by C. G. Pringle in the Valley of 
Mexico, Federal District, 19 October, 1896, no. 7327 (type, in herb. 
Gray), and in fields near Toluca, 26 September, 1892, no. 5257, also at 
an earlier date by Schaffner in mountains near Santa Angela. Neat oe 
_—-M. bibracteatum, Wats., but differing markedly in the contour and cuneate 
__ base of the leaves as well as in its prostrate several-stemmed habit. 
