Parr 1, 1922] AMBROSIACEAE > 37 
‘ 
39. Franseria ilicifolia A. Gray, Proc. Am. Acad 11: 77. 1876. 
Gaertneria ilicifolia Kuntze, Rev. Gen. 339. 1891. 
A shrubby perennial, about 1 m. high; branches hirsute as well as glandular-hispidulous; 
leaves sessile, somewhat clasping, ovate in outline, coarsely dentate with spine-tipped teeth, 
4-6 cm. long, dark-green, strongly veiny and reticulate, hispidulous; staminate involucres 
peduncled, above the sessile pistillate ones; peduncles spreading, 5-10 mm. long; involucre 
saucer-shaped, 1.5 cm. broad or more, hirsutulous; lobes longer than the disk; corolla campanu- 
late, with an obconic base; pistillate involucres subtended by several narrowly lanceolate 
leaves; fruit about 1 cm. long, 2-celled; beaks 2, stout, about 4 mm. long. 
TYPE LOCALITY: Great Cafion of the Tantillas Mountains, near the border of Lower California. 
DISTRIBUTION: Arizona, southern California, and Lower California. 
12. *XANTHIDM 1..Sp: Pl. 897.1753. 
Acanthoxanthium Fourr. Ann. Soc. Linn. Lyon II. 17: 110. 1869. 
Annual herbs, branched, coarse, commonly scabrous or spinose, monoecious, sporadic. 
Leaves alternate, slender-petioled, more or less lobed or rarely incised, usually punctate with 
numerous small resinous dots. Heads unisexual. Staminate heads uppermost, many-flow- 
ered; involucre subglobose; bracts separate and disposed in 1-3 series; receptacle cylindric, 
chaffy; corolla tubular, clavate, 5-toothed at the apex; filaments monadelphous, the anthers 
free, converging, not caudate at base, having incurved-mucronate appendages at the apex; 
style simple, slender, more or less dilated at the apex; achene rudimentary. Pistillate heads 
bur-like; involucre gamophyllous, closed or rarely gaping, cylindric or ovoid or even subglobose, 
aculeate with hooked or very rarely straight prickles, 2-celled, commonly 2-beaked at the 
apex; corollas absent; branches of the style exserted from the beaks; achenes linear or even 
ovate, compressed, more or less fleshy-thickened, slender-beaked at the apex, smooth, pro- 
duced singly in the unequal chambers of the involucre, there persisting until germination. 
Type species, Xanthium strumarium LL. 
Leaves attenuate at both ends; axils armed with tripartite spines; 
prickles cygneous-hooked at the apex. 1. X. spinosum. 
Leaves cordate, ovate, or subtriangulate; axils without spines; prick- 
les simply (not doubly) hooked or straight at the apex. 
Mature fruits less than 2.5 cm. long and 2 cm. wide, including prickles 
and beaks. 
Prickles few and remote (20-50). 
Fruits small, their bodies less than 1.5 cm. long and 6 mm. wide. 
Mature fruits greenish. 
Mature fruits commonly yellowish or reddish. 
Body of fruit narrowly cylindric. 
Prickles arcuate for about their upper half. ie 
Prickles straight except at the hooked apex. 8. 
Body of fruit ovoid or oblong. 
Prickles somewhat slender, the body of the fruit 
commonly 5-6 mm. thick. 9. X. Wootoni. 
Prickles of cartilaginous appearance, thick, .the 
body of the fruit about 8 mm. thick. 13. X. calvum. 
Fruits large, their bodies 1.5—-1.7 em. long and 6-7 mm. wide; 
prickles 8-10 mm. long. 10. X. cenchroides. 
Prickles more numerous. 
Fruits glabrous or subglabrous. 
Body of the fruit ovoid-oblong. 
Prickles not conspicuously thickened at the base. * 
Beaks short (about 2 mm. long), thick. 2. X. strumarium. 
Beaks longer (3-6 mm. long), more slender. 
Prickles not closely grouped together, straight. 3. X. chinense. 
Prickles closely grouped together, arcuate. 
Prickles equal or subequal (4-6 mm. long); 
beaks 3.5—5 mm. long. 6. X. arcuatum. 
Prickles usually unequal, certain ones near 
the beak very long (8-10 mm.); beaks 5-7 
mm. long. 11. X. inflexum. 
Prickles short (usually about 2 mm. long), thickened at 
the base. 14. X. palustre. 
Body of the fruit commonly cylindric. 
Leaves acutely lobed; fruits delicate; prickles slender, 
2.5-3.5 mm. long. 4. X. cylindricum. 
tN 
bd 
. Slyumarium. 
. Curvescens. 
. leptocarpum. 
bb 
*By CHARLES FREDERICK MILLSPAUGH and Eari EDWARD SHERFF. 
