The Manual of the Botany of the Northern United States / Including the District East of the Mississippi and North of North Carolina and Tennessee

by Asa Gray

[*][*] Calyx thin, inflated in fruit, obscurely nerved, 3–5-lobed, open.

27. Physostegia. Calyx 5-toothed or 5-lobed. Anther cells parallel.

28. Synandra. Calyx almost equally 4-lobed! Anther cells widely divergent.

[*][*][*] Calyx of firmer texture, distinctly 5–10-nerved or striate, 5–10-toothed.

[+] Stamens included in the short corolla-tube, its upper lip merely concave.

29. Marrubium. Calyx tubular, 5–10-nerved, and with 5 or 10 awl-shaped teeth.

[+][+] Stamens ascending under the galeate upper lip of the corolla.

[++] Stamens not deflexed after anthesis; naturalized from the Old World.

30. Ballota. Calyx somewhat funnel-form, expanding above into a spreading 5-toothed border. Nutlets roundish at top. Upper lip of the corolla erect.

31. Phlomis. Calyx tubular, the 5 teeth abruptly awned. Upper lip of the corolla arched.