464 PROCEEDINGS OP THE AMERICAN ACADEMY. 



Cumaral, Colombia, Andre, no. 1120, to British Guiana and tropical 

 Brazil, where apparently common. 



+- ■*- Leaves narrowed to a petiole or an exauriculate base : stems solitary. 

 -w Leaves rhombic to elliptic-oblong, obscurely toothed, undivided. 



30. M. FLACCiDUM, Benth. Vidensk. Meddel. 1852, 8G. M. tenellum, 

 var. jiaccidum, Benth. Bot. Sulph. 115 (1844). — Nicaragua near 

 Granada, Oersted; Costa Rica, San Francisco de Guadalupe, Tonduz, 

 nos. 7187, 8498; Tepic, Mexico, Hinds, Palmer, no. 1814 (starved 

 specimens). 



•w- -i-t- Leaves narrow, linear-oblong and imlobed or deeply cleft into narrowly oblong 



segments. 



31. M. HispiDUM, HBK. Nov. Gen. & Spec. iv. 273, t. 399 (1820). 

 M. coronopifuUum, 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 Uha Mountains, Pringle ; Sonora, 

 JVrifjhi, no. 1205; Chihuahua, Pringle, no. 297; Durango, Palmer, no. 

 486 (coll. of 1896) ; San Luis Potosi, Parry & Palmer, no. 4441 ; 

 Jalisco, 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 31. sericeum, Lag. 



•^ -1- -^ 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, entire or obsoletely 

 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 aud hispidulous upon the nerves beneath, 1.2 to 

 2.5 cm. long, 1 to 1.6 cm. 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 or less 

 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. Nearest 

 M. bihrarf.eatum., Wats., but differing markedly in the contour and cuneate 

 base of the leaves as well as in its prostrate several-stemmed habit. 



