42 NORTH AMERICAN FLORA [VOLUME 33 
TYPE LOCALITY: Vicinity of Palo Alto, California. 
DISTRIBUTION: California. 
ILLUSTRATIONS: Field Mus. Publ. Bot. 4: pl. 7, f. 13; pl. 9, f. 11-12; pl. 12. 
14. Xanthium palustre Greene, Pittonia 4: 63. 1899. 
Stem glabrous or slightly scabrous, sometimes reddish, often minutely purple-maculate 
lengthwise, probably 0.5—1 m. high; leaves 0.8-3 dm. long including the pecioles; petioles 
equaling or exceeding the blades; blades ovate-cordate or deltoid, dentate, more or less lobed, 
scabrous; body of the fruit greenish-brown, finally thick-oblong and shining, glandular but 
scarcely pubescent, about 1.8 cm. long and 8-9 mm. thick; beaks short, thick, pubescent, in- 
curved above, often somewhat hooked at the apex, 3-5 mm. long; prickles numerous but 
scarcely crowded, short, glandular and often sparingly pubescent toward the thick base, 
slender and glabrous above, hooked at the apex, 2-2.5 (rarely 3-3.5 or even up to 4) mm. 
long. 
TYPE LOCALITY: Suisun Marsh, California. 
DISTRIBUTION: California. 
ILLUSTRATIONS: Field Mus. Publ. Bot. 4: pl. 7, f. 14; pl. 9, f. 13-15. 
15. Xanthium australe Millsp. & Sherff, Field Mus. Publ. Bot. 
acca0s ~ 1919" 
Stem scabrous, more or less punctate lengthwise with small linear spots, probably 0.5-1 
m. high; leaves 0.8-2 dm. long including the petioles; petioles and blades about equal; blades 
petiolate, 3-nerved, deltoid-cordate, often obscurely lobed, dentate, scabrous; body of the 
fruit ovoid-subglobose, somewhat sparsely glandular-pubescent or glabrate, 0.9-1.1 em. long 
and 6-7 mm. thick (or even 1.3-1.5 cm. long and 8—9 mm. thick on a Chilean specimen); beaks 
attenuate, straight or slightly inflexed, hooked or almost straight at the apex, pubescent be- 
low, 6-9 mm. long; prickles crowded, slender, straight or slightly arcuate, shortly and some- 
what sparsely pubescent below (a specimen from Chile has certain prickles glandular and not 
pubescent), glabrous above, hooked at the apex, 4-5 mm. long. 
TYPE LOCALITY: Vicinity of La Barra, 8 kilometers east of Tampico, Tamaulipas. 
DISTRIBUTION: Mexico; also in Paraguay and Chile. 
ILLUSTRATIONS: Field Mus. Publ. Bot. 4: pl. 7, f. 15; pl. 9, f. 16-18; pl. 13. 
16. Xanthium echinatum Murr. Commentationes Gott. 6: 32. 1785. 
Xanthium maculatum Raf. Am. Jour. Sci. 1: 151. 1819. 
Stems scabrous or scabrous-hispid, purple-maculate, 3-6 dm. high; leaves 0.6—2.3 dm. 
long including the petioles; petioles nearly equaling or even exceeding the blades; blades 
scabrous, commonly cordate and obtusely lobate, obtusely and remotely dentate or serrate; 
body of fruit thick-oval or rarely subglobose, glandular-hispid, finally 1.6—2 em. long and 0.8-1 
em. thick; beaks stout, incurved, more often hooked at the apex, hispid below, 3-5 mm. long; 
prickles slender, straight or arcuate, hispid at the base (or upward as far as the middle), 
smooth above, more often hooked at the apex, about equaling the beaks. 
TYPE LOCALITY: New York. 
DISTRIBUTION: Quebec to New Jersey, and (apparently adventive) in Virginia, Ontario, North 
Dakota, and Missouri. 
ILLUSTRATIONS: Commentationes Gott. 6: pl. 4; Rob. & Fern. Man. f. 989; Field Mus. Publ. 
Bot. 4: pl. 7, f. 16; pl. 9, f. 19-21. 
17. Xanthium italicum Moretti, Giorn. Fis. II. 5: 326. 1822. 
Xanthium varians Greene, Pittonia 4:59. 1899. 
Xanthium glanduliferum Greene, Pittonia 4: 61. 1899. 
Xanthium commune Britton, Man. 912. 1901. 
Xanthium Macounii Britton, Man. 913. 1901. 
Stems branched, scabrous, often lengthwise-punctate with dark-purple linear dots, 3-10 
(-18) dm. high; leaves 0.8-3 dm. long including the petioles; petioles nearly equaling or 
even exceeding the blades; blades cordate or widely ovate, lobed, dentate, scabrous; body of 
the fruit cylindric, oblong or ovoid, but more often broadly oblong, glandular-pubescent, 
1.3-1.8 cm. long, 6-8 mm. thick; beaks commonly incurved and hooked at the apex, hispid, 
