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1 Corolla lobes white, 4-10 mm long, spreading, spatulate to obovate, rounded at the apex; flowering in early spring (rarely to early summer)
..2 Mid-cauline scale leaves opposite; corolla lobes rounded at the apex, abruptly narrowed to a mucro, their margins erose (uncommonly entire); anthers 0.5-1.1 mm long; style slender with stigmas connivent; capsule dehiscing medially
....3 Plants relatively short (avg. 14.3 cm); stems usually purple and often stout; calyx sinuses frequently rounded; stamens frequently purplish
......4 Stems occasionally twining; corolla lobes usually oblong-lanceolate, 2.9–5.2 (mean 4.1) mm long
......4 Stems strictly erect; corolla lobes usually ovate acuminate, 1.9–3.2 (mean 2.6) mm long