100 NORTH AMERICAN FLORA [Volume 34 



4-5 mm. high, 3 mm. broad; bracts 6-8, narrowly oblong, scarious-margined ; ray-flowers 

 7 or 8; ligules 3 mm. long, usually flesh-colored above, rose and with darker veins beneath, 

 the margins white; disk-corollas pale-yellow, about 3 mm. long; tube very short, much shorter 

 than the funnelform throat; achenes 2.5 mm. long, angled, clavate, glabrous; pappus wanting. 



Type locality: Mojave Desert, California. 

 Distribution: Mojave Desert. 



Subtribe 12. TETRANEURANAE. Heads mostly radiate, rarely dis- 

 coid. Involucre usually hemispheric or nearly so, rarely campanulate; bracts 

 narrow (except in Plateilema), erect or ascending (more spreading in Ryd- 

 bergia), rarely with loose tips but not reflexed. Ray-flowers pistillate, perfect; 

 ligules yellow, usually broad, rather strongly veined. Disk-flowers hermaphro- 

 dite, fertile or in Phimmcra sterile, mostly yellow; corolla-tube short, usually 

 glandular, usually less than one-fifth the length of the tubular, tubular-funnel- 

 form, or tubular-campanulate throat. Achenes obpyramidal, distinctly angled, 

 only 2-3 times as long as broad, pubescent with long ascending hairs, usually 

 densely so. Pappus of mostly 5 scarious squamellae. 



Squamellae of the pappus dissected into numerous bristles; plant white- 



floccose; heads discoid. 58. Trichoptilium. 



Squamellae of the pappus not dissected; plant not floccose; heads usually 

 radiate. 

 Bracts ovate, all united at the base; leaves pinnately round-lobed, 



resembling leaves of the white oak. 59. Plateilema. 



Bracts narrower, the inner ones at least distinct. 

 All bracts distinct. 



Bracts soft and herbaceous, not awn-tipped. 



Bracts few; corolla flesh-colored; rays wanting. (Page 64.) 45. ChamaEchaenactis. 

 Bracts numerous; corollas yellow; rays usually present. 

 Leaves entire; squamellae short, obtuse or abruptly 



contracted into a point. 60. Tetraneuris. 



Leaves pinnatifid; squamellae linear-lanceolate, attenu- 

 ate but not awn-tipped. 61. Rydbergia. 

 Bracts rather stiff and the inner awn-pointed. 62. Macdougalia. 

 Outer bracts united below; leaves usually pinnatifid with narrow 

 divisions. 

 Disk-flowers fertile. 63. Hymenoxys. 

 Disk-flowers sterile. 64. Plummera. 



58. TRICHOPTILIUM A. Gray, in Torr. Bot. Mex. Bound. Surv. 



97. 1859. 



Low and spreading floccose annuals. Leaves alternate or the lower opposite, incised- 

 dentate. Heads solitary at the ends of the branches, peduncled, discoid. Involucre hemi- 

 spheric; bracts about 20, in 2 subequal series, the inner narrower and thinner, all flat. Re- 

 ceptacle flat, naked. Ray-flowers wanting. Disk-flowers hermaphrodite, fertile; corolla- 

 tube very short; throat elongate, trumpet-shaped; lobes short, spreading, the marginal ones 

 somewhat enlarged. Anther-tips oblong-lanceolate. Style-branches linear, obtuse. Achenes 

 obpyramidal, villous-hirsute. Pappus-squamellae 5, lanceolate, dissected into unequal 

 bristles. 



Type species, Psathyrotes incisa A. Gray. 



1. Trichoptilium incisum A. Gray, in Torr. Bot. Mex. Bound. Surv. 



97. 1859. 

 Psathyrotes incisa A. Gray, Mem. Am. Acad. II. 5: 322. 1854. 



A floccose annual, branched from the base; stem 1-1.5 dm. high, villous-floccose; leaves 

 oblanceolate or spatulate, narrowed below into a margined petiole, 1-5 cm. long, densely 

 white-floccose, acute, incised-dentate; peduncles 4-7 cm. long, glandular-puberulent; involucre 

 7 mm. high, 10-12 mm. broad; bracts lanceolate or oblanceolate, acute or the inner obtuse; 

 flowers 30-40; corollas 4 mm. long, puberulent; achenes 3 mm. long, 1 mm. broad, obpyra- 

 midal, 5-angled and striate; pappus nearly as long as the corolla. 



Tvric locality: Californian Desert near the Colorado River. 

 DISTRIBUTION: Southern California, Arizona, and Lower California. 

 Illustrations: Pacif. R. R. Rep. 5: pi. 5; E. & P. Nat. Pfl. 4 5 :/. 125, L. 



