Virginia Bluebells, white form (Mertensia virginica)
The sky-blue form is most common, but Bluebells come in a range of colors from white through pale lilac to pink as well as blue. The other colors are rare, but common enough that in a large patch you’ll usually find some of them. This plant grew in the Squaw Run valley in Fox Chapel, where it was blooming in late April.
Gray describes the genus and the species:
MERTENSIA Roth. LUNGWORT
Corolla longer than the deeply 5-cleft or 5-parted calyx, naked, or with 5 small glandular folds or appendages in the open throat. Anthers oblong or arrow-shaped. Style long and thread-form. Nutlets ovoid, fleshy when fresh, smooth or wrinkled, obliquely attached by a prominent internal angle ; the scar small. Smooth or soft-hairy perennial herbs, with pale and entire leaves, and handsome purplish-blue (rarely white) flowers, in loose and short panicled or corymbed raceme-like clusters, only the lower one leafy-bracted; pedicels slender. (Named for Franz Karl Mertens, a German botanist.)
* Corolla trumpet-shaped, with spreading nearly entire limb and naked throat; filaments slender, exserted; hypogynous disk 2-lobed.
M. virginica (L.) Link. (VIRGINIAN COWSLIP, BLUEBELLS.) Very smooth, pale, erect, 2-6 dm. high; leaves obovate, veiny, those at the root 1-1.5 dm. long, petioled; corolla trumpet-shaped, 2-2.5 cm. long, many times exceeding the calyx, light blue (pinkish in bud), rarely white; nutlets dull and roughish. Alluvial banks, N. Y. and Ont. to Neb., and southw. Apr., May.