1. Calystegia macounii (Greene) Brummitt

Pl. 363 f; Map 1577

Stems mostly 40–90 cm long, scrambling or trailing, usually twining only toward the tip (rarely not twining), moderately to densely pubescent with short, velvety hairs. Leaves mostly long-petiolate, moderately to densely pubescent with short, velvety hairs, the petiole more than 1/2 as long as the midvein of the accompanying leaf blade. Leaf blades 2–6(–8) cm long, oblong-ovate to ovate, broadly rounded to less commonly bluntly pointed at the tip, deeply cordate at the base, the sinus usually V-shaped, the basal lobes entire (lacking additional shallow lobes along the upper portion), not spreading (oriented more or less toward the leaf base), broadly rounded to less commonly slightly angled and bluntly pointed. Flowers solitary in the axils of leaves, positioned mostly above the stem midpoint. Bracts 18–25 mm long, usually strongly overlapping, often strongly inflated, ovate to oblong-ovate, bluntly or sharply pointed at the tip, sparsely to moderately pubescent with short hairs. Sepals 10–12 mm long, ovate to elliptic. Corollas not doubled, 4–6 cm long, white or rarely pinkish purple. Fruits 10–15 mm long. Seeds 4–6 mm long. May–July.

Uncommon and widely scattered in the state. (Montana to Arizona east to Minnesota and Louisiana and locally east to Virginia and Georgia; Canada). Banks of streams; also pastures, fallow fields, and gardens.

Plants of C. macounii were known as Convolvulus sepium f. malacophyllus or C. spithamaea in much of the older botanical literature (Steyermark, 1963). At the species and subspecies level, the epithet malacophylla applies to a different taxon endemic to California, Calystegia malacophylla (Greene) Munz. Records from the eastern half of the state may represent introduced populations. The main range of C. macounii is in the central third of the country. However, the range of this species in Missouri is not well understood, and it has probably been undercollected by botanists who have mistakenly assumed plants to be C. sepium. Austin (1997) noted that this species tends to be the earliest in the complex to bloom.