498 COMPOSITAE (COMPOSITE FAMILY) 



10. ISOCOMA Nutt. 



Herbaceous or suffruticose, commonly more or less balsamic- viscid. Leaves 

 not punctate, sometimes dentate or pinnatifid. Heads several-many-flowered ; 

 bracts of the involucre either coriaceous or firm-chartaceous and usually some- 

 what herbaceous or thickened at the obtuse or barely acute apex, all strictly 

 appressed and well imbricated, but the vertical ranks inconspicuous. Style- 

 appendages subulate-lanceolate or broader, shorter than the stigmatic portion. 

 Achenes short, sericeous-pubescent. Pappus of numerous sordid bristles, the 

 innermost longest and often distinctly flattened. 



1. Isocoma Wrightii (Gray) Rydb. Bull. Torr. Bot. Club 33: 152. 1906. 

 Commonly glabrous or nearly so; stems rather strict and slender, 3-5 dm. 

 high from a lignescent base: leaves thickish, narrowly linear, entire, some- 

 times lower ones sparingly laciniate-dentate, margins either smooth or spar- 

 ingly hirtello-scabrous: heads 8-10 mm. high, 7-15-flowered, usually numer- 

 ous and crowded in a corymbiform cyme; bracts of the involucre oval-oblong 

 to broadly lanceolate, obtuse; the back at or near the apex usually greenish, 

 but no definite tip. Banks of streams and in saline soil; western Texas to 

 Arizona and in (?) Colorado. 



11. SIDERANTHUS Fraser 



Annual or perennial herbs or shrubs. Leaves alternate; blades flat, 

 spinulose-toothed or lobed or pinnatifid, commonly sessile. Heads radiate 

 and showy or rarely discoid. Involucres hemispheric or campanulate, many- 

 flowered; bracts in several series, the inner successively larger. Receptacle 

 flat or nearly so, naked, generally pitted. Ray-flowers pistillate; disk- 

 flowers mostly perfect. Corollas yellow; tube scarcely dilated into a throat. 

 Anthers obtuse at the base. Stigmas flattened, with lanceolate appendages. 

 Achenes obtuse, pubescent, mostly 8-10-nerved. Pappus of 1-3 series of 

 many unequal hair-like bristles, persistent. (Eriocarpum Nutt.) This and 

 the following seven genera were all included in the Aplopappus of the Manual. 



Annuals. 



Leaves spinescently toothed; stem stout, simple . . . . 1. S. annuus. 

 Leaves pinnatifid; stem slender, branched . . . . . 2. S. gracilis. 

 Perennials. 



Leaves spinescently toothed; stems numerous from a woody caudex 3. S. grindelioides. 

 Leaves pinnatifid; stems from a woody caudex; canescently tomen- 



tose, cinereous, or glabrate. 



Involucres somewhat glandular; leaves pinnatifid to sub-entire . 4. S. australis. 

 Involucres not glandular; all the leaves pinnatifid . . . 5. S. spinulosus. 



1. Sideranthus annuus Rydb. Bull. Torr. Bot. Club 31: 653. 1904. An- 

 nual, 3-7 dm. high, viscid-glandular and pubescent or puberulent: leaves 

 lanceolate or narrowly oblong, incisely pinnatifid or dentate with salient 

 narrow teeth: heads somewhat cymosely paniculate, 10-14 mm. high, usually 

 naked-pedunculate; bracts of the involucre linear-subulate and with slender 

 spreading green tips: stronger bristles of the fulvous or at length rufous pap- 

 pus numerous: rays golden-yellow. Aplopappus rubiginosus. On the plains; 

 Kansas and Nebraska to Colorado. 



2. Sideranthus gracilis (Nutt.) Rydb. Fl. Col. 344. 1906. Annual or be- 

 coming lignescent at base and more enduring, canescently pubescent, oc- 

 casionally glabrate and glandular-scabrous; stems 1-3 dm. high, much 

 branched: leaves linear or the lowest spatulate, pinnatifid, or the upper few- 

 toothed or entire, tipped or also sparsely fringed with long and slender bris- 

 tles: heads 8-12 mm. high; bracts of the involucre mostly setaceous-tipped: 

 pappus rigid; the larger bristles manifestly dilated below. New Mexico and 

 Colorado to Utah and Arizona. 



3. Sideranthus grindelioides (Nutt.) Brit. Man. 932. 1901. Perennial 

 by a deep woody root, finely pubescent; stems tufted, simple, erect, 1-3 dm. 

 high: leaves oblong-lanceolate to spatulate, sessile, or the lower petioled, 



