244 NORTH AMERICAN FLORA [VoLUME 34 
3. Crossostephium insulare Rydberg, sp. nov. 
A shrub, 0.5—2 dm. high; branches densely canescent; leaves 5-10 cm. long, very fleshy, 
densely canescent, the lower irregularly pinnatifid into linear divisions, the upper entire; 
leaves and their segments 1-3 mm. wide; heads mostly solitary at the ends of short leafy 
branches, more or less nodding; involucre hemispheric, 3 mm. high, 4-5 mm. broad; bracts 
15-18, in 3 series, all oval, densely canescent on the back, more or less scarious-margined, 
especially the innermost, the outer only slightly shorter; ray-flowers 10-15; corollas cylindric, 
slightly flattened, minutely 3—4-toothed, 1 mm. long, glandular-granuliferous; disk-flowers 
30-40; corollas cylindro-campanulate, 5-toothed, fully 1.5 mm. long; achenes with 3-5 thick 
ribs, becoming glutinous in wetting; pappus coroniform. 
Type collected along Pot’s Trail, San Clemente Island, California, June, 1903, Blanche Trask 
286 (herb. N. Y. Bot. Gard.). 
DISTRIBUTION: San Clemente and San Nicolas islands, California. 
16. PICROTHAMNUS Nutt. Trans. Am. Phil. Soc. II. 7: 417. 
1841. 
Low spiny shrubs. Leaves alternate, pedately divided and again lobed, with narrow 
divisions. Heads solitary or in small racemes in the axils and at the ends of the short branches, 
apparently discoid, the marginal flowers without ligules. Involucre saucer-shaped; bracts 
obovate-cuneate, scarious, in two more or less distinct subequal series. Receptacle naked. 
Marginal flowers (functionally ray-flowers) few, pistillate, fertile; corolla short, deeply 2-cleft, 
villous; style long-exserted, with long linear obtuse branches. Disk-flowers hermaphrodite 
but sterile; corollas with a narrow obconic tube, a turbinate throat, and a 5-lobed limb, 
densely arachnoid-hairy; anthers oblong, with subulate tips and obtuse bases; style slender, 
with a peltate, erose stigma. Achenes ellipsoid, densely arachnoid-hairy. 
Type species, Picrothamnus desertorum Nutt. 
1. Picrothamnus desertorum Nutt. Trans. Am. Phil. Soc. II. 7: 
417. 1841. 
Artemisia spinescens D.C. Eaton, in S. Wats. Bot. King’s Expl. 180. 1871. 
A low spiny villous shrub, 1-3 dm. high; leaves crowded, villous, 1-2 cm. long, pedately 
3-5-divided and the divisions usually 3-cleft into linear-spatulate divisions; heads few; in- 
volucre 2 mm. high, 4-5 mm. broad; bracts 5-8, obovate-cuneate, villous; ray-flowers 1—4; 
corollas less than 1 mm. long; style 2-2.5 mm. long; disk-flowers 2.5-3 mm. long; style included; 
achenes fully 1.5 mm. long. 
TYPE LocaLity: Rocky Mountain plains, in arid deserts, towards the north sources of the 
Platte. 
DISTRIBUTION: Wyoming to New Mexico, Oregon, and California. 
ILLUSTRATION: S. Wats. Bot. King’s Expl. pl. 19, f. 15-21. 
17. ARTEMISIA L,. Sp. Pl. 845. 1753. 
Absinthium (Tourn.) Lam. Fl. Fr. 2: 45. 1778. 
Abrotanum (Tourn.) Neck. Elem. 1: 98. 1790. 
Oligosporus Cass. Bull. Soc. Philom. 1817: 33. 1817. 
Perennial or annual herbs, or shrubs, usually bitter-aromatic. Leaves alternate, mostly 
dissected, lobed, or toothed, sometimes entire. Heads small, most commonly panicled and 
nodding when young, apparently discoid, the marginal flowers without ligules or wanting. 
Involucre campanulate to hemispheric; bracts in 2—4 series, at least the inner ones more or 
less scarious. Receptacle naked or hairy, convex or conic. Marginal flowers (functionally 
ray-flowers) pistillate and fertile or wanting; corollas cylindric or subcylindric and somewhat 
tapering upwards, 2-3-, rarely 4-toothed, often somewhat oblique; stamens wanting; style 
more or less exserted, 2-cleft; style-branches linear-filiform and subterete to oblong and some- 
what flattened. Disk-flowers hermaphrodite, fertile or sterile; corollas campanulate, funnel- 
form, or trumpet-shaped, 5-toothed, regular; anthers longer than the short filaments, oblong, 
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