This is the original Pansy, still so called in many places; it is every bit as colorful as our garden pansies, but smaller. It often escapes from plantings, and can occasionally establish itself in sidewalk cracks or vacant lots. The plants above and below, for example, sprouted from sidewalk cracks on the South Side. Although it is associated with spring, it can bloom occasionally throughout the year.
Gray (with revisions by Brainerd) describes the genus and the species:
VIOLA [Tourn.] L. VIOLET. HEART’S-EASE.
Petals somewhat unequal, the lower one spurred at the base. Stamens
closely surrounding the ovary, often slightly cohering with each other;
the two lower bearing spurs which project into the spur of the corolla.
Besides these conspicuous blossoms, which appear in spring, others are
produced later, on shorter peduncles or on runners, often concealed under
the leaves; these never open nor develop petals, but are fertilized in the
bud and are far more fruitful than the ordinary blossoms. — The closely
allied species of the same section, when growing together, often hybridize
with each other, producing forms that are confusing to the student not
familiar with the specific types. The hybrids commonly display characters
more or less intermediate between those of the parents, and show marked
vegetative vigor but greatly impaired fertility. (The ancient Latin name
of the genus.)
Plants with leafy stems.
Style much enlarged upward into a globose hollow summit with a wide
orifice on the lower side; stipules large, leaf-like, lyrate-pinnatifid.
V. tricolor L. (PANSY, HEART’S-EASE.) Stems angled, 1.5-8 dm. high; lower
leaves roundish or cordate, upper oblong, crenate; flowers large and
widely spreading, variously marked with yellow, white, and purple;
capsules ovoid; seeds brown. — An escape from cultivation, rarely
persisting. (Introd. from Eu.)
We should note that a Wikimedia Commons editor identified the plants below as Viola × wittrockiana, the garden pansy, and renamed the files. Father Pitt is not convinced; he thinks they are Viola tricolor, but he has been wrong more than once before.