4. Ipomoea lacunosa L. (small white morning glory)

Pl. 367 a–c; Map 1599

Plants annual. Stems 10–300 cm long, glabrous or sparsely and inconspicuously hairy. Leaves long-petiolate. Leaf blades 2–8 cm long, unlobed or shallowly to deeply 3(5)-lobed, the lobes triangular, broadly ovate to ovate-triangular in overall outline, tapered to a sharply pointed tip, shallowly to deeply cordate at the base, glabrous or both surfaces sparsely to moderately short-hairy, the margins otherwise entire. Flowers solitary or more commonly in loose clusters of 2–6, the stalks glabrous, often appearing somewhat warty when dry. Sepals similar in size and shape or the outer 2 slightly shorter and narrower, (8–)10–14 mm long, lanceolate to narrowly ovate, or narrowed or tapered to a sharply pointed tip, the margins sparsely to moderately pubescent with spreading hairs. Corollas 1.2–2.2 cm long, funnelform to slightly bell-shaped, the tube widened gradually toward the tip, all white (for pink-flowered individuals, see the discussion of hybrids below). Stamens not exserted. Ovary usually 2-locular, the stigma 2-lobed. Fruits globose or slightly depressed-globose, the main body 10–14 mm long, the persistent style 0.8–1.5 mm long, moderately to densely pubescent with relatively long, often curly, spreading hairs. Seeds 5–6 mm long, the surface glabrous. 2n=30. August–October (rarely as early as June).

Common nearly throughout the state (eastern U.S. west to Iowa, Kansas, and Texas; Canada). Banks of streams and rivers, margins of ponds and lakes, moist depressions of upland prairies, and fens; also crop fields, fallow fields, old fields, pastures, fencerows, ditches, railroads, roadsides, and open, disturbed areas.

Austin (1978) and Abel and Austin (1981) interpreted plants assignable to I. lacunosa f. purpurata Fernald as representing introgressive hybrids between I. lacunosa and I. cordato-triloba Dennst. (I. trichocarpa Elliott), a southeastern species that has not been documented from Missouri. These fertile hybrids, known as I. Hleucantha Jacq., are common in the southeastern United States, and the sporadic occurrences nearly throughout the Missouri range of I. lacunosa may originally have been introduced from there. They differ from I. lacunosa in having slightly larger flowers with light pink corollas.