ParT 1, 1922] AMBROSIACEAE 41 
about 8 mm. long; prickles abouc 25, straight or nearly so, hispid below, glabrous above, 
hooked at the apex, 8-10 mm. long. 
TYPE LocaALity: Near Ferris, Texas. 
DISTRIBUTION: Texas. 
ILLUSTRATIONS: Field Mus. Publ. Bot. 4: pl. 7, f. 10; pl. 8, f. 37-39. 
11. Xanthium inflexum Mackenzie & Bush, Rep. Missouri Bot. 
Gard. 16: 106. 1905. 
Stem glabrous, or on the upper part more or less scabrous, branched, 1-1.5 m. high; leaves 
0.8-2.5 dm. long, the petioles and blades subequal; blades cordate or ovate-cordate, 3- or 
somewhat 5-lobed, irregularly serrate or dentate, weakly or strongly scabrous; body of the 
fruit oblong-elliptic or ovate-oblong, armed with somewhat numerous prickles, otherwise 
glabrous or sparsely glandular, 1.3-1.7 \-2) cm. long and 6-7.5 mm. thick; beaks strong, 
when mature abruptly bent at the middle, strongly incurved, hooked and often touching or 
overlapping at the apex, glandular-pubescent below, commonly 5—7 mm. long; prickles slender, 
rather close together, commonly arcuate, hooked at the apex, glandular-pubescent or finally 
glabrous below, 4.5—-6.5 mm. long, commonly with certain abnormal ones 8-10 mm. long near 
the beaks. 
TYPE LOCALITY: Courtney, Missouri. 
DISTRIBUTION: Southwestern Illinois to Arkansas. 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. ed. 2. f. 4136: Field Mus. Publ. Bot. 4: pl. 7, f. 11; 
pl. 9, f. 1-4. 
12. Xanthium pennsylvanicum Wallr. Beitr. Bot. 1: 236. 1844. 
Xanthium pennsylvanicum glandulosum Wallr. Beitr. Bot. 1: 236. 1844. 
Xanthium pennsylvanicum eglandulosum Wallr. Beitr. Bot. 1: 236. 1844. 
Xanthium saccharatum Wallr. Beitr. Bot. 1: 238. 1844. 
Xanthium affine Greene, Pittonia 4: 60. 1899. 
Xanthium californicum Greene, Pittonia 4: 62. 1899. 
Xanthium acutum Greene, Pittonia 4:62. 1899. 
Xanthium crassifolium Millsp. & Sherff, Field Mus. Publ. Bot.4:4. 1918. 
Xanthium acutilobum Millsp. & Sherff, Field Mus. Publ. Bot. 4:6. 1918. 
Stem scabrous, or smooth below, 3-9 dm. high; leaves 0.7-2 dm. long including the 
petioles, the petioles equaling or exceeding the blades; blades deltoid-ovate or cordate, dentate, 
often acutely 3—5-lobed, scabrous on both sides; body of the fruit narrowly cylindric, oblong, 
ovate-fusiform, or even ovoid, but commonly more or less cylindric, glabrous or glabrate or 
covered with short glandular hairs, 1-2 cm. long and 5—8 mm. thick; beaks slender or thick, 
glandular-pubescent below, toward the apex glabrous and more often incurved, at the apex 
hooked, 4-6 mm. long; prickles somewhat remote and rather coarse (or more rarely close to- 
gether and slender), glandular and often sparsely pubescent toward the base, otherwise gla- 
brous, hooked at the apex, sometimes purplish-tinged, 3-7 mm. long. 
TYPE LocaLity: Asheville, North Carolina. 
DISTRIBUTION: Massachusetts to Washington, and southward to Florida and California; per- 
haps also in Mexico; frequent in the Hawaiian Islands. 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. f. 3600; ed. 2. f. 4137; Field Mus. Publ. Bot. 4: pl. 4; 
pl. 7, f. 12; pl. 9, f. 5-10. 
13. Xanthium calvum Millsp. & Sherff, Field Mus. Publ. Bot. 4: 
soe OTS: 
Stem erect, becoming reddish, often lengthwise-dotted with small purplish spots, some- 
what scabrous, or even glabrous below, about 4-9 dm. high; leaves 0.6-2 dm. long including 
the petioles; petioles equaling the blades; blades ovate-cordate or ovate-triangulate, at the 
base either orbiculate or truncate or cordate, commonly darker green, crenate-dentate. often 
dentately lobed, somewhat scabrous; fruits few or numerous, the thick body ovate-fusiform, 
brown, subacute at each end, shortly and very sparingly pubescent, glandular, 1.5-1.8 cm. 
long and about 8 mm. thick; beaks thick and strong below, glandular-pubescent at the base, 
commonly inflexed at the middle, more or less hooked at the apex, 3-5 mm. long; prickles sub- 
remote, straight, glandular or rarely pubescent at the base, otherwise glabrous, 4-6 mm. long; 
beaks and prickles commonly purple-tinged, especially toward apex. 
