WOOTON AND STANDLEY FLORA OF NEW MEXICO. 749 



129. BARTLETTIA A. Gray. 



Slender annual, nearly glabrous, with long-petiolate rounded repand -dentate 

 leaves and long-pedunculate, rather large heads, these heterogamous, radiate; invo- 

 lucre campanulate, of 12 to 14 oblong-lanceolate bracts in 2 or 3 series; achenes 

 cuneate-oblong, compressed ; pappus of numerous unequal bristles in a single series. 



1. Bartlettia scaposa A. Gray, Mem. Amer. Acad. n. ser. 5: 323. 1854. 

 Type locality: On a prairie near Corralitas, Chihuahua. 

 Range: Southern New Mexico, south into Mexico. 

 New Mexico: Lordsburg (A. Davidson 1422). 



130. MESADENIA Raf. 



Perennial herb; leaves thrice pinnatifid into narrow segments; heads 10 to 15 mm. 

 high, numerous, in corymbiform cymes; involucre turbinate, of a single series of 5 

 or 6 narrow bracts; flowers 5 or 6, with white corollas, none radiate; achenes glabrous. 



1. Mesadenia decomposita (A. Gray) Standley. 

 Cacalia decomposita A. Gray, PI. Wright. 2: 99. 1853. 

 Type locality: Mountains east of Santa Cruz, Sonora. 



Range : Southern Arizona and southwestern New Mexico to northern Mexico. 

 New Mexico: San Luis Mountains (Meams 2219, 527, 531). 



131. CENTAUREA L. Star thistle. 



Tall, usually simple-stemmed annual with alteiTiate, spatulate to oblong-lanceolate, 

 entire or denticulate leaves and large showy heads of tubular flowers; involucre cam- 

 panulate, the bracts appressed in many series, pectinate; outer corollas pink or pur- 

 plish, enlarged and radiant, the inner ones ochroleucous; achenes compressed, smooth; 

 pappus of several series of unequal bristles. 



1. Centaurea americana Nutt. Joum. Acad. Phila. 2: 117. 1821. 



Plectocephalus americanus Don in Sweet, Brit. Flower Gard. 2: pi. 5^.1823-29. 



Type locality: "On the banks of streams, and in denudated alluvial situations, 

 throughout the plains or praiiies of the upper part of Arkansas temtory." 



Range: Arkansas and Louisiana to Arizona and southward. 



New Mexico: Socorro; Mogollon Mountains; Mangas Springs; G O S Ranch; 

 Mesilla; White Mountains; mountains north of Santa Rita. Moist slopes and along 

 streams, in the Upper Sonoran and Transition zones. 



132. CIRSIUM Hill. Thistle. 



Coarse biennial or perennial herbs with prickly, often pinnatifid, sessile, alternate 

 leaves and large heads, the latter soKtarj^, racemose, or clustered at the ends of the 

 branches; flowers all tubular, perfect; bracts of the involucre imbricated in many 

 ranks, mostly tipped ■with prickles; receptacle clothed with soft bristles; achenes 

 oblong or obovoid, compressed, smooth; pappus of numerous plumose bristles united 

 into a ring at the base, deciduous. 



KEY TO the species. 



Bracts deep pmple, reflexed for half their length, not arachnoid . 1 . C. vinaceum. 

 Bracts not purplish or if so only at the very tips, when reflexed 

 more or less arachnoid . 



Plants acaulescent 2. C. acaulescens. 



Plants not acaulescent. 



At least some of the bricts pectinate-ciliate with weak 

 spines; flowers greenish yellow. 



