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.