44 FIELD MUSEUM OF NATURAL HISTORY BOTANY, VOL. IV. 



gracilibus, remisse fere usque ad apicem pilis mollibus longiusculis 

 vestitis, rectis aut subrectis, ad apicem nunc dimidia parte eorum 

 hamosa, nunc vix uno aculeo hamoso, plerumque 6-9 mm. longis. 



DISTRIBUTION: New York (where apparently adventive) ; Wisconsin, 

 North Dakota and Nebraska. 



SPECIMENS EXAMINED: NEW YORK: Whitehall, Dresden Trestle, 

 Stewart H. Burnham 28 (Hb. Gray). WISCONSIN: Brown County, 

 Preble, Baird's Creek, Sept. 26, 1899, /. H. Schuette (Hb. Gray; Hb. U. S. 

 751759; the latter a rather immature and indistinctive specimen). 

 NORTH DAKOTA: near Fargo, Sept. 4, 1893, Edward L. Greene (Hb. 

 Greene 19835; type) ; Minot, along Souris River, Dr. J. Lunell 80 (Hb. 

 Gray); Burleigh County, Bismarck, Aug. 23, 1913, idem (Hb. Greene 

 23707). NEBRASKA: Red Cloud, Rev. J. M. Bates 4747 (Hb. Gray). 



It is with some hesitation that this species is here retained. The 

 fruiting burs, when slightly immature, resemble those of X. italicum. 

 When fully ripe, they appear to be intermediate between those on cer- 

 tain forms of X. pennsylvanicum Wallr. and those on certain forms of 

 X. speciosum Kearney. The brown, ripe burs have a body more or 

 less narrowly cylindrical; the prickles are mostly long and very delicate; 

 their hairs are soft and fine. However, as the specimens examined agree 

 very well among themselves, interference with the status of the species 

 seems scarcely wise or desirable at the present time. 



19. XANTHIUM OVIFORME Wallr., Beitr. Bot. i 11 : 240. 1844. 

 X. silphiifolium Greene, Pittonia 4: 60. 1899. 



Caulis simplex, infra levis, supra scabridus, 3-7 dm. altus. Folia 

 membranacea, indivisa, deltoideo-ovata, interdum vix trinervia, 

 inaequaliter sinuato-dentata, utrinque concoloria et setulis minutis 

 adpressis albidis aspera, ad basim vel orbiculata vel truncata vel 

 cordata, petiolis adjectis 0.7-2 dm. longa, petiolis laminis subaequan- 

 tibus. Fructus (PI. VII, f. 19; PI. X, ff. 1-3) non multi, demum maximi, 

 plerumque singulatim dispositi; fructuum corpore oblongo-ovato, 

 glanduloso-hispido aut rariter glabriusculo, aculeis armato, demum 

 circum 2 cm. longo et 1.2 cm. crasso; rostris validis, crassis, hispidis, 

 supra incurvatis, ad apicem valde uncinatis, circum 8 mm. longis; 

 aculeis remotis aut subremotis (aut fere confertis), validis, arcuatis et 

 corniformibus, fere usque ad apicem ferrugineo-hispidis (saltern ad 

 tergum et latera), ad apicem valde hamosis, ad faciem ventralem infe- 

 rioribus plerumque canaliculatis, (5-) 7-10 mm. longis. 



DISTRIBUTION: Washington and probably Oregon; also adventive, 

 formerly at least, in southwestern Illinois. 



SPECIMENS EXAMINED: WASHINGTON: Wawawai, C. V. Piper 3575 

 (Hb. Gray); Kittitas County, Rock Island, along water-courses, 

 Sandberg and Leiberg 446 (Hb. Gray); West Klickitat County, Sept. 28, 

 1883, sandy banks of the Columbia River, W. N. Suksdorf (Hb. Field 



