26b. var. sphaerocarpon

P. sphaerocarpon var. inflatum (Scribn. & J.G. Sm.) Hitchc. & Chase

Flowering stems with the nodes with short, appressed hairs. Inflorescence about as long as wide. 2n=18. May–September (vernal), July–November (autumnal).

Scattered in the southern two‑thirds of the state (eastern U.S. west to Illinois, Missouri, and Texas). Upland prairies, glades, mesic to dry upland forests, and less commonly banks of streams, usually on acidic substrates; also roadsides and open, disturbed areas.

In addition to the characters in the key above, plants of var. sphaerocarpon also tend to have the uppermost leaves with relatively short blades (2–11 cm long, 3–15 mm wide) and the middle and lower leaves all of about equal lengths.