This occurs mostly in the central Mississippi Valley, usually in woods on damp, circumneutral to slightly acid, clayey terraces (D). Although generally distinct, it is sometimes hard to distinguish from affinis or communis, and it may intergrade with them; see notes under those species. V. langloisii Greene is typically a more southern species, and that name has been used for some "missouriensis" as mapped here, or perhaps for transitions to other species (Sm; Correll & Johnston 1970; see also colls. at NY). If combined with missouriensis following Gil-ad (1997), langloisii may have nomenclatural priority due to its earlier publication; but H. Ballard (in prep.) has treated them as distinct species. Based on varied descriptions of missouriensis (F, St, Gil-ad 1997; H. Ballard, in prep.), distinctive characters are as follows. Sepals tend to be finely ciliate over most or all of the margin (versus over just the lower half in affinis); flowers tend to be relatively pale lilac or lavender around the darker center; and the spurred petal is not distinctly bearded (like cucullata but not affinis). The lowest sepal is oblong to ovate-lanceolate, with obtuse to rounded apex; and auricles are short and rounded (like affinis but not cucullata). Leaves are completely glabrous (versus slightly hairy above on lobes in affinis), deltoid-ovate and relatively narrow when fully developed, sometimes coarsely dentate at base, and attentuate with slight concavity to the apex (versus more broadly ovate-orbicular and acute or abruptly pointed). V. missouriensis may also be confused with less hairy forms of sororia, but it can then be distinguished (H. Ballard, in prep.) by its seeds: medium orange-brown, unspotted or often with minute dark brown to blackish spots as in affinis (versus light gray to medium grayish-brown with weak to dark rectangular blotches), and relatively small as in affinis (1.5-2.2 × 1.0-1.3 mm versus 1.5-2.6 × 1.0-1.6 mm).