44 NORTH AMERICAN FLORA [VOLUME 33 
TYPE LOCALITY: Between Paint Rock and Del Rio, along French Broad River, Cocke County, 
Tennessee. 
DISTRIBUTION: Tennessee to South Dakota and Texas; adventive in Maine and Vermont. 
ILLUSTRATIONS: Rob. & Fern. Man. f. 988; Britt. & Brown Ill. Fl. ed. 2. f. 4133; Field Mus. 
Publ. Bot. 4: pl. 7, f. 20; pl. 10, f. 4-6. 
21. Xanthium campestre Greene, Pittonia 4: 61. 1899. 
Stem somewhat scabrous above, often spotted with short purple lines, 5-8 dm. high; 
leaves 6-17 cm. long including the petioles; petioles almost equaling the blades; blades thick- 
ish, subdeltoid, dentate or serrate, not noticeably lobed, truncate or cordate at base, scabrous 
above, scabrous-pubescent below; fruits very large, for the most part singly disposed, ovoid- 
conic; bodies not often visible among the numerous prickles, becoming about 2.3—2.6 cm. long 
and 1—1.3 cm. thick; beaks widely divergent, thick and pubescent below, glabrate and slenderly 
hooked, 6-7 mm. long; prickles terete, arcuate, ferrugineous-hispid below, glabrous above and 
hooked at the apex, about 5 mm. long; whole fruit (prickles and beaks included) finally 2.8-3.5 
em. long and 2-2.5 cm. wide. 
TYPE LOCALITY: Chico, California. 
DISTRIBUTION: California. 
ILLUSTRATIONS: Field Mus. Publ. Bot. 4: pl. 7, f. 21; pl. 10, f. 7-8. 
DOUBTFUL AND EXCLUDED SPECIES 
XANTHIUM AMERICANUM Walt. Fl. Car. 231. 1788. Inadequately described. The 
name amounts to little more than a nomen nudum. 
XANTHIUM CANADENSE Mill. Gard. Dict. ed. 8. Xanthium no. 2. 1768. (Not X. cana- 
dense of recent American authors.) This appears clearly referable, by synonymy, to X. 
orientale L,. (See footnote 1, Field Mus. Publ. Bot. 4: 20. 1919.) 
XANTHIUM CAVANILLESIL Schouw, Ind. Sem. Hort. Haun. 1849: 14. 1849; Ann. Sci. 
Nat. III. 12: 357. 1849° Probably referable, as to plate cited (Cav. Ic. pl. 221), either to 
X. chinense Mill. or to X. italicum Moretti. (See Field Mus. Publ. Bot. 4: 40, footnote 1. 1919.) 
XANTHIUM CRASSUM Raf. Med. Fl. 2: 275. 1830. Nomen nudum. 
XANTHIUM UNDULATUM Raf. Med. FI. 2: 275. 1830. Nomen nudum. 
XANTHIUM LAEVIGATUM Muhl.; Wallr. Beitr. Bot.1: 231. 1844. This was founded upon 
a specimen collected by Muhlenberg and deposited in the Willdenow Herbarium; we are un- , 
able to identify this from the description. 
XANTHIUM ORIENTALE L. A European species with fruits somewhat similar to those of 
X. curvescens but coarser and more pubescent among the prickles; not known to occur in 
North America. 
