WOOTON" AND STANDLEY FLOE A OF NEW MEXICO. 631 



KEY TO THE SPECIES. 



Low, 20 cm. high or less; heads solitary, 20 to 30-flowered, the flowers 



purplish.. 1. P. nana. 



Tall, 60 cm. or more high; heads corymbose or paniculate, 5 to 12- 

 flowered, the flowers nearly white. 

 Heads 5 or 6-flowered; bracts obtuse or acutish, glabrous on the 



back 2. P. wrightii. 



Heads 8 to 12-flowered; bracts abruptly acuminate, scaberulous on 



the back 3. P. thurberi. 



1. Perezianana A. Gray, Mem. Amer. Acad. n. eer. 4: 111. 1849. 

 Type locality: Near Chihuahua, Mexico. 



Range: Western Texas to southern Arizona and southward. 



New Mexico: Cliff; Laguna Colorado; Carrizalillo Mountains; Dog Spring; 

 Deming; San Marcial; Organ Mountains; White Sands; Knowles; Nogal; La Luz 

 Canyon. Dry plains and hills, in the Lower Sonoran Zone. 



2. Perezia wrightii A. Gray, PI. Wright. 1: 127. 1852. 



Type locality: " On the Rio Seco and westward; also on the Rio Grande, Texas." 



Range: Western Texas to southern Arizona and southward. 



New Mexico: Mangas Springs; Florida Mountains; Dona Ana Mountains; Organ 

 Mountains; Tortugas Mountain. Diy hills and ravines, in the Lower and Upper 

 Sonoran zones. 



3. Perezia thurberi A. Gray, Mem. Amer. Acad. n. eer. 5: 324. 1854. 

 Type locality: Rocky Mils, near Santa Cruz, Sonora. 



Range: Southern New Mexico and Arizona, southward into Mexico. 

 New Mexico: Dog Spring; San Luis Mountains. 



3. TPvIXIS P. Br. 



Low woody perennial with entire or denticulate alternate lanceolate leaves and 

 corymbose medium-sized heads of yellow flowers; involucres muny-flowered, the 

 bracts 8 to 12, equal, in a single series, subtended by a few bractlike leaves; achenes 

 slender, with a tapering summit; pappus yellowish, of capillary bristles. 



1. Trixis californica Kellogg, Proc. Calif. Acad. 2: 182./. 53. 1862. 



Type locality: Cedros Island, Lower California. 



Range: Western Texas to Arizona and Mexico. 



New Mexico: Black Range; Mangas Springs; Bear Mountains; Dog Spring; near 

 White Water; Dona Ana Mountains; Organ Mountains; Tortugas Mountain; south of 

 Roswell. Rocky canyons and hills, in the Lower and Upper Sonoran zones. 



143. AMBROSIACEAE. Ragweed Family. 



Annual or perennial herbs or shrubs with alternate leaves; flowers email, aggre- 

 gated on a receptacle, surrounded by an involucre, the staminate and pistillate in 



the sai ir separate heads; involucra] bracts few, distinct or united, those of the 



pistillate flowers often QUtlike or burlike at inaiurity <>r winged; stamens usually 5, 

 distinct; corollas all tubular; ovary 1-celled; stigmas 2, hairy or brashlike at the 

 apex. 



can to i'ii 1 1 i;i m-.ka. 



Staminate and pistillate (lowers in the same heads, tin* 



latter u-w (rarely solitary or none) in the margins. 



A.chenes flattened, wing-margined; involucre with 



I or 2 inner enlarged scarious bracts 1. Dicobia (p. 032). 



