860 CARDUACEAE 



linear-lanceolate, acuminate, squarrose; ligules numerous. 1-1.5 cm. long. Aplo- 

 pappus ciliatus DC. River banks and hillsides: Mo. Tex. Colo. Plain. 



17. SIDERANTHUS Nutt. IRON PLANT. 



Perennial or annual herbs, rarely suffruticose at the base. Leaves alternate, 

 with spinulose-tipped lobes or teeth. Heads radiate, or in two species discoid. 

 Involucres campanulate or hemispheric, many-flowered ; bracts well imbricate, 

 in 3-5 series, appressed or with loose tips, green; receptacle flat, naked, usually 

 pitted. Ray-flowers pistillate, or in two species wanting; ligules yellow. Disk- 

 corollas yellow; tube scarcely dilated into a distinct throat. Anthers obtuse at 

 the base. Style-branches flattened, with lanceolate appendages. Achenes ob- 

 tuse, pubescent, mostly 8-10-nerved. Pappus of many unequal hair-like bristles 

 in 1-3 series, persistent. 



Leaves spinescent-toothed, not pinnatifld. 



Heads discoid ; perennials, with woody caudex. \ 



Heads peduncled. 1. S. grindelioides. 



Heads sessile. 2. S. aberrans. 



Heads radiate; annuals. 



Leavas oblanceolate, spinulose-tipped; plant more or less viscid. 3. S. annnus. 

 Leaves linear-oblanceolate, bristle- tipped; plant strigose. 4. S. gracilis. 



Leaves pinnatifid; perennials, with a short woody base; achenes somewhat flattened. 

 Stem more or less floccose or cinereous, especially when young. 



Plant cinereous pubescent, more or less glandular. 5. S. australis. 



Plant more or less floccose, not at all glandular. 6. S. spinulosus. 



Plant neither floccose nor cinereous. 



Plant perfectly glabrous or sparingly glandular-puberulent. 7. S. glaberrimus. 

 Plant flnelj- puberulent, or hispid. 



Heads hemispheric; bracts slightly glandular. ,8. S. puberulus. 



Heads somewhat turbinate; bracts densely glandular-puberulent. 



9. S. turbinellus. 



1. S. grindelioides (Nutt.) Rydb. Low cespitose perennial; stems erect, 

 1-3 dm. high, somewhat pubescent; leaves thick, obovate or oblanceolate, spinu- 

 lose-serrate, 1-3 cm. long, more or less crisp-hirsute or strigose; involucres hemi- 

 spheric, 6-7 mm. high, 1 cm. broad; bracts lanceolate, puberulent; achenes some- 

 what flattened. Eriocarpum grindelioides Nutt. Aplopappus Nuttallii T. & G. 

 Dry plains and hills: Sask. Neb. N.M. Ariz. Nev.Alta. Plain Sub- 

 mont. Je-Au. 



2. S. aberrans (A. Nels.) Rydb. Perennial, with a creeping rootstock; stems 

 erect, 5-10 cm. long, glandular-pubescent; leaves obovate or oblong, glandular- 

 puberulent, or the lower ovate, 1-3 cm. long, sparingly cuspidate-toothed on the 

 margins; heads 1-4, subsessile, 9-14 mm. high; bracts broadly linear, acute, 

 green and glandular-viscid at the apex; achenes cylindric-fusiform, 3 mm. long. 

 Macronema aberrans A. Nels. Mountains: Ida. Mont. Au. 



3. S. annuus Rydb. Annual; stem simple below, branched above, more or 

 less glandular-pubescent; leaves oblanceolate, spinulose-dentate, 3-6 cm. long; 

 heads corymbose; involucres hemispheric, about 8 mm. high, viscid-puberulent ; 

 bracts linear-lanceolate, acuminate; ligules light yellow, 5-6 mm. long; achenes 

 obtusely 5-angled. Aplopappus rubiginosus A. Gray, in part. Sandy places: 

 Neb. Colo. Tex. Plain. 



4. S. gracilis (Nutt.) Rydb. Annual, branched, becoming woody at the 

 base; stems 2-4 dm. high, hispid-strigose ; leaves linear-oblanceolate to spatulate 

 in outline, coarsely dentate or somewhat pinnatifid; teeth tipped with long 

 bristles; involucres 6 mm. high; bracts linear, spinulose-tipped, strigose; ligules 

 5-6 mm. long, light yellow. Dieteria gracilis Nutt. A. gracilis A. Gray. Dry 

 hills: s Colo. Tex. Ariz. Calif.; Mex. Son.Submont. My-S. 



5. S. australis (Greene) Rydb. Stem 2-4 dm. high; leaves pinnatifid, 2-7 

 cm. long; segments linear or oblong, spinulose-tipped, entire or toothed; involucres 

 6 mm. high; bracts linear, puberulent, spine-tipped; ligules 5-6 mm. long, yellow. 

 Eriocarpum australe Greene. Dry soil : Colo. Tex. N.M. Ariz. e Utah; Mex. 

 Son. Submont. Ap-Je. 



6. S. spinulosus (Pursh) Sweet. Stem 1-4 dm. high, branched; leaves 1-3 

 cm. long, pinnatifid; segments linear or oblong, usually toothed or pinnately 



