APRIL, 1919. XANTHIUM MILLSPAUGH AND SHERFF. 31 



glanduloso-pubescentibus, plerumque 5-7 mm. longis (auctores "circ. 

 10 mm. longis" dixerunt inaccurate); aculeis tenuibus, subconfertis, 

 plerumque arcuatis, ad apicem hamosis, infra glanduloso-pubescentibus 

 aut demum glabratis, 4.5-6.5 mm. longis, saepequibusdamabnormalibus 

 versus rostra longissimis (8-10 mm.). 



DISTRIBUTION: Southwestern Illinois to Arkansas. 



SPECIMENS EXAMINED: MASSACHUSETTS: Cambridge, Botanical 

 Garden, Oct., 1848, from seed collected by Engelmann (presumably 

 collected the preceding year at East St. Louis, Illinois) Asa Gray (two 

 sheets in Hb. Gray, bearing nos. 172, 1720 and 174). ILLINOIS: East 

 St. Louis, river bank, Sept., 1847, George Engelmann (Hb. Mo. 85551); 

 MISSOURI: Courtney, in bottoms, B. F. Busk 869 (Hb. Gray; Hb. Mo. 

 85519; an atypic form apparently hybridized with X. pennsylvanicum 

 Wallr.) ; Courtney, in bottoms, idem 1804 and 1805 (Hb. Mo. 85409 and 

 85531 respectively); Courtney, in bottoms, idem 1806 (Hb. Mo. 85522; 

 Hb. Gray) ; Courtney, in bottoms, idem 1916 (Hb. Mo. 85520 and 85521 ; 

 Hb. Gray; type material). ARKANSAS: Fulton, along river, B. F. 

 Bush 1026 (Hb. Mo. 85554 and 85555; Hb. Gray; a form approaching 

 X. pennsylvanicum Wallr., the burs having long, somewhat delicate 

 beaks, which are not decidedly inflexed). 



Fortunately, we have been able to examine fairly numerous speci- 

 mens of this little known species. The burs have a body averaging of 

 larger size than in X. chinense Mill. ; in shape and appearance the body 

 is intermediate between that in X. chinense Mill, and that in X. penn- 

 sylvanicum Wallr. The prickles are long, as in X. speciosum Kearney, 

 but more slender, much smoother and somewhat less abundant. 



12. X. PENNSYLVANICUM Wallr. 1 Beitr. Bot. i n : 236. 1844.; Britton 

 and Brown Illustr. Fl., Edit. II, 3: 346, f. 4137. 1913. 



X. pennsylvanicum vars. glandulosum and eglandulosum Wallr. 

 loc. cit. 



X. saccharatum Wallr. loc. cit. 238; 



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



X. californicum Greene and X. acutum Greene, loc. cit. 62. 

 Caulis subtenuis scabridus, aut infra levis, 3-9 dm. altus. Folia 

 deltoideo-ovata aut cordata, dentata, saepe acute 3~5-lobata, utrinque 

 setulis minutis adpressis scabra, petiolis adjectis 0.7-2 dm. longa, petiolis 

 laminas subaequantibus aut excedentibus. Fructuum (PI. VII, f. 12; 

 PI. IX, ff. 5-10) corpus nunc anguste cylindricum, nunc oblongum, 

 nunc ovato-fusiforme, nunc etiam ovoideum, sed plerumque plus 

 minusve cylindricum, glabrum aut glabratum aut pilis glandulosis 

 brevibus vestitum, 1-2 cm. longum et 5-8 mm. crassum, aculeis arma- 

 tum; rostris tenuibus aut crassis, infra glanduloso-pubescentibus, versus 



1 The name as originally given by Wallroth was spelled X. pensylvanicum. 

 Fernald (Rhodora 19: 70. 1917) is inclined to retain the old spelling in such cases 

 and gives the historical reasons for pursuing such a course. 



