1. Arnoglossum atriplicifolium (L.) H. Rob. (pale Indian plantain)

Cacalia atriplicifolia L.

Pl. 296 a, b; Map 1246

Rootstock not tuberous-thickened, but with somewhat fleshy roots. Stems 1.2–3.0 m tall, circular in cross-section, rounded or with fine longitudinal grooves, glaucous. Leaves herbaceous in texture. Basal and lower leaves long-petiolate, the blades 15–45 cm long, broadly triangular-ovate to kidney-shaped or heart-shaped, often shallowly palmately lobed, the tip and lobes usually broadly pointed, usually broadly cordate at the base, the margins otherwise irregularly toothed, the venation palmate with mostly 7–10 main veins, glabrous, the undersurface conspicuously glaucous. Upper leaves short-petiolate, ovate to ovate-triangular (the uppermost sometimes narrowly obovate), coarsely toothed, tapered at the base. Involucre 7–9 mm long, the inner bracts rounded dorsally, uniformly greenish white, rarely darker along the margins, the outer series usually absent (rarely with 1 or 2 minute bracts toward the tip of the stalk of the head). Corollas 8–10 mm long, white, cream-colored, or rarely somewhat pinkish-tinged. 2n=50, 52, 54, 56. June–October.

Scattered nearly throughout the state (eastern U.S. west to Nebraska and Oklahoma). Bottomland forests, mesic upland forests, bases and ledges of bluffs, and banks of streams and rivers; also occasionally pastures, railroads, and roadsides.

This species, with its interesting foliage, would make an attractive addition to the garden, but it appears not to be widely available at nurseries. Steyermark (1963) suggested that it prefers neutral to somewhat limy soils.

The leaves of A. atriplicifolium tend to be somewhat more angular than those of A. reniforme. The lower leaves are often more coarsely toothed, with lobes that are usually somewhat deeper and more angular. They are, however, quite variable in size and lobing. Arnoglossum atriplicifolium grows in the shade, as does A. reniforme, but it also seems to tolerate sunnier sites than those in which that species is found. Coleman (1965) studied a sterile hybrid between A. atriplicifolium and A. reniforme (as Cacalia atriplicifolia and C. muhlenbergii) from a site in southern Indiana where the two parents were growing in proximity. Gleason and Cronquist (1991) also mentioned hybridization between these two species. Although not yet confirmed from Missouri, this hybrid, which is morphologically intermediate between the two parental species, eventually may be discovered in the state as isolated individuals at sites where the parents are growing mixed or adjacent to one another.