CAMPANULACEAE (Bellflower Family)

Contributed by David J. Bogler

Plants mostly perennial herbs (sometimes shrubby elsewhere), usually with milky sap. Leaves usually alternate, simple, the margins entire, toothed, or lobed, lacking stipules. Inflorescences terminal spikes or racemes, axillary clusters or solitary flowers, or the flowers rarely terminal and solitary. Flowers perfect, epigynous or deeply perigynous. Calyces 5-lobed (sometimes 3- or 4-lobed in cleistogamous flowers), usually actinomorphic, fused to the ovary, the tube sometimes extending slightly past the ovary, persistent, sometimes with a short, reflexed appendage between each of the lobes. Corollas more or less 5-lobed, actinomorphic and funnel-shaped to bell-shaped or saucer-shaped, or zygomorphic and strongly 2-lipped, and usually split along the apparently upper side (through which the stamens and style are exserted), white to purple, blue, or red. Stamens 5, the filaments distinct or united into a tube toward the tip. Anthers attached at their bases, distinct or fused into a tube surrounding the style. Pistil 1 per flower, of 2–5 fused carpels. Ovary inferior or less commonly only partially inferior, with 1 or 2–5 locules, the placentation parietal (if 1 locule) or axile. Style 1 per flower, elongate, the stigma 2–5-lobed. Ovules numerous. Fruits capsules, dehiscing by apical or lateral pores, slits, or longitudinally. Seeds numerous, minute. Sixty to 70 genera, about 2,000 species, nearly worldwide.

The Campanulaceae are recognized by the combination of alternate leaves, milky latex, well-developed corolla with united petals, inferior to half-inferior ovary, often specialized pollination mechanisms, and capsular fruits with numerous seeds. The family comprises two distinct subfamilies that some authors have maintained as separate families (Rosatti, 1986). The subfamily Campanuloideae has actinomorphic flowers, nontwisted flower stalks, most commonly three carpels and stigma lobes, free filaments and anthers, and pollen grains with spiny ornamentation. The Lobelioideae have strongly zygomorphic flowers borne on a stalk that is twisted so that the upper lip of the flower is positioned basally at flowering (resupinate, as in most orchids), most commonly 2 carpels and stigma lobes, the filaments fused into a tube toward the tip, the anthers fused into a ring, and pollen grains with a network of ridges rather than spines. Recent molecular studies (Cosner et al., 1994) have supported maintaining both groups as a single family. The flowers of species in the Lobelioideae are functionally similar to those of the Asteraceae in that the stigma elongates through the center of the ring of fused anthers, with a brush of hairs near the style tip pushing the pollen out of the flower, and the stigma lobes do not spread and become receptive until after the pollen has been released. This mechanism promotes outcrossing between flowers.

The genus Sphenoclea is sometimes included in the Campanulaceae. The present treatment follows that of Rosatti (1986) in treating this group as a separate family, Sphenocleaceae (to be included in the third volume of the present work). Steyermark (1963) noted the existence of a specimen of the commonly cultivated ornamental, Platycodon grandiflorum (Jacq.) A. DC. (balloon flower), at the herbarium of William Jewell College, Liberty, Missouri, but excluded the species from the Missouri flora in the belief that it was an isolated, nonpersistent escape from an adjacent planting. This specimen was not examined during the present study. Platycodon resembles Campanula but differs in its larger flowers (corollas to 45 mm long) and strongly inflated buds. It has been recorded as an escape sporadically from New York to North Carolina, but it has not persisted outside of cultivation yet in any midwestern state.