1186 CARDUACEAE 



2. Sideranthus phylloc6phalus (DC.) Small. Stems pubescent, 1-4 dm. tall, 

 branched at the base and often diffuse : leaf-blades 2-8 cm. long, those of thecauline leaves 

 jiinnatifid, the segments tipped with bristle-like teeth : heads snowy, solitary and sessile at 

 the ends of the leafy branches : involucres 6-9 mm. higli, the outer bracts more or less 

 foliaceous : ray-flowers with narrow ligules 8-11 mm. long. 



On sandy beaches, Texas and adjacent Mexico. Summer and fall. 



3. Sideranthus rubiginosus (T. & G. ) Britton. Stems viscid and pubescent, 2-9 

 dm. tall, branching : leaf-blades oblong to lanceolate, 3-5 cm. long, remotely dentate with 

 awn-tipped teeth, mostly sessile : heads terminating naked peduncles, corymbose : involucres 

 campanulate, 7-9 mm. high ; bracts lanceolate to linear, acuminate, with green spreading 

 tips, glandular without : ray flowers with oblong or slightly oblanceolate ligules 6-7 mm. 

 long. 



On plains and prairies, Nebraslca and Colorado, soutli to Texas. Fall. 



4. Sideranthus aureus (A. Gray) Small. Stem thinly lanuginous and glandular, 

 1-2.5 dm. tall, branched at the base, the branches sometimes decumbent : leaves rather 

 few ; blades linear or slightly linear-spatulate, 1-2.5 cm. long, pinnatifid, dentate at least 

 near the base : involucres campanulate, about 1 cm. high ; bracts linear to linear-oblong, 

 glandular, blunt, the outer with green tips, the inner almost scarious : ray-flowers 18-25 ; 

 ligules barely 1 cm. long, golden yellow : achenes turbinate, with 10-12 stout pappus 

 bristles. \_Aplopcq)pus aureus A. Gray. ] 



On prairies, Houston, Texas. Summer. 



5. Sideranthus glaberrimus Rydb. Stems more or less branched from the woody 

 base, the branches mostly ascending, 1-4 dm. long, corymbose above, glabrous or merely a 

 little puberulent, but wholly destitute of woolly pubescence : leaf-blades pinnatifid or 

 pinnately parted, the segments usually entire, acute : involucres about 5 mm. high ; 

 bracts linear-lanceolate to linear, glabrous or essentially so, most of them terminating in 

 pale subulate tips : ray-flowers with ligules 4-7 mm. long. 



In dry soil, South Dakota to Wyoming and the Indian Territory. Spring to fall. 



6. Sideranthus Cotula Small. Similar to *S'. glaberrimus in habit. Stems and 

 branches copiously glandular-pubescent : leaf-blades 1-2 cm. long, finely bipinnatifid, the 

 segments mostly less than 1 mm. wide : involucres 4-5 mm. high ; bracts glandular-pubes- 

 cent, acute or acuminate : ray-flowers with narrow ligules 4-6 mm. long. 



In dry soil, the Indian Territory. Summer. 



7. Sideranthus Machaeranthera Small. Stems clustered on a woody base, about 1.5 

 dm. tall, sparingly corymbose above, finely glandular-pubescent : leaf-blades much larger 

 and coarser than those of .S'. Cotula, 2.5-4.5 cm. long: involucres 5-6 mm. high; bracts 

 minutely glandular, acuminate : ray-flowers with ligules 6-9 mm. long. 



In dry soil, along the Brazos River, Texas. Summer. 



8. Sideranthus australis (Greene) Rydb. Stems branched at the woody base, the 

 branches 1-4 dm. tall, mostly ascending, thinly pale-canescent, sparingly branched above : 

 leaf-blades 1-2.5 cm. long, coarsely toothed or pinnatifid, the teeth or segments slenderly 

 spine-tipped : involucres 5-6 mm. high ; bracts more or less subulate-tipped, pubescent : 

 ray-flowers with ligules about 1 cm. long. 



In dry or rocky soil, Texas to New Mexico and adjacent Mexico. Spring to fall. 



9. Sideranthus spinulosus (Pursh) Sweet. Stems woolly-canescent, 1-3 dm. tall, 

 commonly branched : leaf-blades 1-3 cm. long, pinnately parted, the segments mostly 

 toothed or pinnatifid : involucres 8-9 mm. high ; bracts appressed, oblong-lanceolate to 

 linear, acute : ray-flowers with oblong ligules 5-6 mm. long. 



On plains. Northwest Territory to North Dakota, Texas, Arizona and Mexico. Summer and fall. 



31. ISOCOMA Greene. 

 Herbaceous or woody plants, often with viscid foliage. Leaves alternate : blades en- 

 tire toothed or pinnately parted. Heads radiate, solitary or clustered. Involucres mainly 

 campanulate, several- to many-flowered : bracts leathery or firmer, obtuse or merely acute 

 at the more or less thickened tip, imbricated. Receptacle pitted. Ray-flowers usually 

 several, pistillate. Disk-flowers more numerous than the rays, perfect. Corollas yellow, the 

 throat much inflated. Stigmas somewhat flattened and slightly broadened upward, hairy 

 at the tip. Achenes broadened upward, silky. Pappus of numerous slender barbell ulate 

 bristles. 



Leaf-blades entire or nearly so : bracts of the involucres acute or acutish. 1. I. Drummondii. 



Leaf-blades pinnately parted : bracts of the involucres obtuse. 2. I. coroiwpijolia. 



