1. Campanula americana L. (tall bellflower)

Campanulastrum americanum (L.) Small

Pl. 330 f–h; Map 1404

Plants robust annuals or biennials, with a short taproot. Stems 50–200 cm long, erect or strongly ascending, unbranched or occasionally sparsely branched toward the tip, glabrous or less commonly sparsely to moderately hairy toward the tip. Leaves gradually reduced from near the stem base to the tip, with a slender, often winged petiole 1–5 cm long, the uppermost leaves usually sessile. Leaf blades 5–16 cm long, 2–6 cm wide, lanceolate to oblong-ovate, usually tapered at the base, tapered to a sharply pointed tip, the margins evenly, relatively finely, and sharply toothed, inconspicuously hairy, the surfaces sparsely hairy, especially along the veins. Inflorescences relatively dense spikelike racemes, the flowers solitary or in clusters of 3 at each node, the lowermost bracts more or less leaflike but most of the bracts reduced (much shorter and narrower than the leaves). Calyx tube 3–4 mm long at flowering, elongating as fruit matures, the lobes 7–12 mm long, 0.8–1.2 mm wide, hairlike to very narrowly triangular. Corollas saucer-shaped, the tube 3–4 mm long, the lobes 6–15 mm long, hairy at the tip, blue. Style 12–15 mm long, strongly exserted from the corolla, elongating and becoming S-shaped (curved from near the base toward the bottom of the flower and arched upward toward the tip) in open flowers, the stigma 3-lobed. Fruits 5–12 mm long, 3–4 mm in diameter, obconic, 3-locular, erect or ascending, dehiscing by 3 round pores near the tip; seeds 0.8–1.2 mm long, 0.8–1.0 mm wide, flattened, often with a thin, winglike margin. 2n=58, 102. July–September.

Forest edges, open, mesic woods, bluffs, disturbed areas, roadsides. Endemic to eastern North America, from southern Canada south to Florida, west to Minnesota and Oklahoma. Abundant in Missouri, this species is easily identified by its stout, tall habit, shortly rotate corolla, and exserted, curved style. It does not appear to be closely related to the other species in the genus and has been considered a separate genus, Campanulastrum, by some authors (Small, 1903). However, critical characters such as the rotate corolla are found in other species of Campanula (Rosatti, 1986).

Pollination in C. americana was described by Shetler (1962). The flowers are protandrous, that is, the pollen matures and is dispersed prior to the maturation and receptivity of the stigmas. Pollen matures in the bud, with the 5 anthers forming a tight column around the terminal part of the style. The anthers shed their pollen on the style, which is equipped with bristly hairs. Once the bud opens, the anthers wither very quickly. A variety of insects, including bees, flies, and butterflies, visit the flowers, attracted by nectar produced at the base of the filaments. When the flower opens, these insects attempt to get at the nectar, rubbing against the pollen-bearing hairs of the style. At about the same time, the style elongates rapidly, develops an S-shaped curve, and the stigmas become receptive to pollen carried from other flowers. Self-pollination might be possible if the unfolding stigma lobes touch the style.