14 FIELD MUSEUM OP NATURAL HISTORY BOTANY, VOL. IV. 



Aculei non valde hispidi. 



Quidam aculei ad fructus rostra longissimi (8-10 

 mm.) ii. X. inflexum 



Aculei aequales aut subaequales: 



Corpus globoso-ovatum, rostris elongatis 



15. X. australe 



Corpus plerumque angustius, rostris non perspicue 

 elongatis 12. X. pennsylvanicum 



Sect. I. ACANTHOXANTHIUM DC. Prodr. 5 : 523. 1836; Acanihoplia 

 Wallr., Beitr. Bot. i n : 241. 1844; Acanthoxanthtum Fourr., 

 pro genere, Ann. Soc. Linn. Lyon., N. Ser. 17 : no. 1869. Invol- 

 ucri fructigeri rostrum saepius unicum aut nullum; fructibus 

 apice conniventibus, clausis; spinis validis ad basim foliorum; 

 foliis numquam cordatis sed basi cuneatis. 



i. XANTHIUM SPINOSUM Linn. Sp. PI. 987. 1753. 



Xanthium xanthocarponWallr. Beitr. Bot. i n :24i. 1844. 



Acanthoxanihium spinosum Fourr. Ann. Soc. Linn. Lyon., N. Ser. 



17 : no. 1869. 



Caulis pubescens, ramosus, erectus aut ascendens, 3-12 dm. altus. 

 Folia lanceolata aut ovato-lanceolata, petiolata, utrinque acuminata 

 aut acuta, 2-4-lobata aut supera integra, infra et ad venas supra 

 canescentia, petiolis adjectis 4-12 cm. longa, axillis spinis gilvis tri- 

 partitis usque ad 2.5 cm. longis munita; petiolis 0.5-2 cm. longis. 

 Fructus (PI. VII, f. i; PI. VIII, ff. 1-3) oblongo-cylindrici, plerumque 

 flavido-virides, pubescentes; rostris tenuibus, levibus, acribus, circ. 

 3 mm. longis, plerumque uno et saepe etiam duobus absentibus; aculeis 

 distinctis aut remotis, ex apice cygneo-curvato in hamum inflexum 

 quartam aculei partem desinentibus. 1 



DISTRIBUTION: Now generally distributed almost throughout the 

 United States; found also in South America, where probably native, 2 

 central Europe, "western Asia, southern Africa and in Australia." 



SPECIMENS EXAMINED : 3 NEW YORK: without locality or date, 

 M. Ruger (Hb. Mo. 720720). NEW JERSEY: Camden, Aug., 1878, 

 Isaac C. Martindale (Hb. Mo. 720837). DISTRICT OF COLUMBIA: vicin. 

 of Washington, waste ground, E. S. Steele 43 (Hb. Mo. 85567 and 

 85568). VIRGINIA: Bedford County, A. H. Curtis 3472 (Hb. Mo. 

 85569); Wythe County, Reed Creek, at base of lower rocks, July 23, 

 1892, John K. Small (Hb. Mo. 85570). FLORIDA: Apalachicola, without 

 date, Dr. A. W. Chapman (Hb. Mo. 783796). ILLINOIS: Mound City, 



1 It may be remarked that in the description we have omitted all reference to 

 achene characters. As the characters of the achene can not be described satisfac- 

 torily from fruits not known to be mature, and as thoroughly mature fruits have 

 not, in all species, been available for dissection, it has been deemed best to omit 

 these characters from all of the specific descriptions. 



2 Cf. Thellung, Mitteil. bot. Mus. Univ. Zurich 58 : 505. 1912. 

 * Many omitted here for lack of space. 



