McAfee and Metcalf — Notes on Cockleburs. 179 



D. Body (0.9-2.5 cm. long — rarely over 2 cm.) narrowly fusi- 

 form or ellipsoidal, usually straight; surface of body 

 smooth or warty-glandular; base of beaks and spines 

 usually glandular- warty or rarely short-pubescent; beaks 

 comparatively longer, more slender, usually straight and 

 more or less divergent. X. chinense. 



DD. Body (1-3.25 cm. long — often over 2.5 cm.) narrowly oblong- 

 ovoid or ovoid-fusiform, often curved; surface of body 

 pubescent, hispid or glandular pubescent; base of beaks 

 and spines usually densely hispid-pubescent; beaks com- 

 paratively shorter, stouter especially at base and often 

 incurved apically. X. pennsylvanicum. 



Annotated List of Species. 



Xanthium spinosum Linnaeus. — Rather rare; apparently has been 

 introduced several times, thrived for a season but failed to become per- 

 manently established; not recorded since 1896; has been collected near 

 Alexandria, Va., in S. W. Washington and D. C. definite locality not given. 



Xanthium chinense Miller. — Abundant in waste ground, cultivated 

 fields and dumps throughout the District and vicinity. Collected near 

 Benning Road, Navy Yard, Anacostia, War College, Water Street, near 

 "I" S. W., Potomac Park, Lincoln Memorial, 29th and "K" streets, N. W., 

 above Aqueduct Bridge, District Line near C. and O. Canal, also from 

 Plummer's Island, Bladensburg and Laurel, Maryland, and Alexandria, 

 Arlington Farm, Rosslyn, Chain Bridge and Cherrydale, Virginia. 



Xanthium pennsylvanicum Wallroth. — Abundant in waste ground, 

 cultivated fields and dumps throughout the District and vicinity. Col- 

 lected near Benning Road, Southeast of Mt. Hamilton, Pennsylvania 

 Avenue Bridge, S. E., Navy Yard, Anacostia, War College, Potomac 

 Flats, Lincoln Memorial, Water Street, near "I" and 14th, S. W., and 33rd 

 Streets, N. W., foot of 27th N. W., and Cleveland Park, also from Plum- 

 mer's Island, Maryland, and Alexandria, Barcroft, Arlington Farm and 

 Rosslyn, Virginia. 



Xanthium italicum Moretti. — Frequent in waste ground. Collected 

 from Benning Road, 19th and Mass. Ave., S. E., and Navy Yard, also 

 Laurel, Maryland, and Alexandria, Arlington Farm and Aqueduct Bridge, 

 Virginia. 



Xanthium speciosum Kearney. — Rare, only a single, but very robust 

 plant found in waste ground along Water Street about 33rd Street, N. W. 



Explanation of Plate 4. 

 Fig. 1. Xanthium spinosum. 

 Fig. 2. Xanthium chinense. 

 Fig. 3. Xanthium pennsylvanicum. 

 Fig. 4. Xanthium speciosum. 

 Fig. 5. Xanthium italicum. 



Figures slightly less than natural size. 



