1302 AMBROSIACEAE 
solitary in each eavity of the bur.—About 40 species, widely distributed.— 
Sum.—CroTBURS. BURWEEDS. COCKLEBURS. 
Body of the bur 1.5-3 cm. lon 
* Bur nc P orn edt OUDCRHISDE hispidulous, or glabrate. 
B e bur broadly fusiform, nearly half as wide 
1. X. americanum. 
Body f the bur almost cylindric, about a third as 
wide as long. 2. X. cylindraceum. 
Bur more or less T hispid, especially on the lower 
part of the spin 
Body of the bur. cylindro. fusiform, about a third as 
wide as long, less than 2 em. long; spines 5-7 mm 
long. 3. X. pennsylvanicum. 
Dody of A ad ellipsoid, half as wide as long or 
nearly 
Body of the bur about 1.5—1.8 cm. long; spines 3 
mm. long. 4, X. echinatum. 
so of d bur about 2.5—3 cm. long; spines 8-11 
lon 5. X. speciosum. 
Body of the hie about 1 em. long. 6. X. echinellum. 
. X. americanum Bo Plant pabo or finely pubescent, 2—13 dm. tall: 
leaf-blades ovate to deltoid, 5-30 e ous om ody of the bur broadly eee 
15-18 mm. long, tion pes with | 100-2 
slender, more or less hooked s spines, whic ^ 
'e 3-4 mm. long, and is equalling. the 
beaks which are straight nearly to the 
apex. p chinense mL & Sherff scarce- 
ly Mil. X. glabratum (DC.) Britton ]— 
Waste- -places, a grounds, E npe 
various provinces, Fla. to , Nebr., and 
Tas SS. 
- Xx. icu ME Millsp. & Sherff. Plant 
ough-puberulent, 5-15 - tall: leaf- 
blades deltoid. ovate, 8—10 b: ng: body 
of the bur almost cylindrie, pem a 125- 
175 ad i x d SP! ines about 3 mm 
tong; - bea long, aa gly i 
rved ae E ‘old fields, and ae grounds, Piedmont, N. C. 
3. X. pennsylvanicum Wallr. Plant rough-pubescent, at least above, 2-6 dm 
tall: leaf-blades ovate to reniform: body of the bur cylindro-fusiform, 15-20 
mm. long, the spines 100—150, n as long as the dia meter of the body; 
beaks 4-6 mm. long, often incurved.—Rich soil, various provinces, Fla. to 
Tex., Minn., Mass., and Va. 
echinatum Murr. ru rough-pubescent, 3-16 dm. tall: leaf-blades 
ovate to deltoid, or reniform: bod of the bur ellipsoid, 15-18 mm. long, his 
pid, the spines 100— 200, sto ut, more or less hooked; beaks 3-5 mm. long, Pont: 
e ved.—Rive r-banks, beaches, and waste-places, various provinces, N. C. 
c Nebr., N. D., and Me. 
5. X. speciosum Kearney. Plant somewhat pubescent, 10-15 dm. tall: leaf- 
blades deltoid-ovate to somewhat reniform: body of the bur 25-30 m E 
pubescent and E beset with 200 or more ineurved spines; beaks 8-1 mn 
long; MUR n Interior Low Plateaus and adj. DEO E 
Tenn. to Tex., Mont., and Mi 
inellum Greene. Plant sparingly hispidulous and the stem striate 
and reddish: leaf- blades broadly cordate, 5-18 em. long and fully as wide, 3- 
