1a. ssp. albiflora
Pl. 475 d
Stems sparsely
prickly. Sepals with the horns 3–5 mm long, unarmed except at the tip. Fruits
oblong in outline to oblong-ellipsoid, the surface with prickles more or less
similar in size, all relatively large and relatively evenly distributed. 2n=28.
June–September
Introduced,
uncommon and widely scattered in the southern half of the state (native of the
southeastern U.S.; introduced north to Missouri, Illinois, and Connecticut).
Railroads, roadsides, and open, disturbed areas.