1. Mitella diphylla L.

Pl. 558 f, g; Map 2601

Plants with short stout rhizomes. Leaves basal and mostly long-petiolate, the apparent flowering stems (actually the main inflorescence stalks) with a single pair of opposite bracteal leaves toward the midpoint, these sessile or short-petiolate, the petioles pubescent with moderate to dense, longer, downward-pointing hairs having minute dark glandular tips and sparse to dense, minute stalked glands. Stipules 1–5 mm long, scalelike, ovate to oblong-ovate, the margins entire to somewhat irregular. Leaf blades 1–9 cm long, slightly longer than to about as long as wide (the flowering stem leaves to about 2 times as long as wide), ovate to nearly circular, the base cordate (often broadly rounded to truncate on flowering stem leaves), the tip rounded or pointed, the margins usually with 3 or less commonly 5 shallow lobes, also finely to coarsely scalloped or toothed, palmately veined with mostly 5 primary veins, the upper surface glabrous or sparsely to moderately hairy, sometimes sparsely glandular toward the base, green, the undersurface sparsely to moderately hairy and glandular, especially along the veins, pale green to grayish green. Inflorescences 10–40 cm long (measured from the rhizome tip), spikelike racemes with 5–20 flowers, erect, long-stalked, moderately to densely pubescent with minute stalked glands below the pair of bracteal leaves, also with longer, spreading to downward-pointing hairs having minute glandular tips. Flowers actinomorphic, subtended by a minute oblong-ovate bract. Hypanthium shallowly bell-shaped, fused to the basal portion of the ovary. Sepals 1.0–1.5 mm long, oblong-triangular, glabrous, greenish white. Petals 2.0–2.5 mm long, deeply pinnately dissected into linear segments, glabrous, white. Stamens 10, much shorter than the calyx, the anthers small, attached at their cordate bases, pale yellow. Ovary 1-locular in the fused portion, the placentation parietal. Styles short, the stigmas crescent-shaped or lozenge-shaped. Fruits 2.5–3.0 mm long, broadly ovoid, 2-beaked, dehiscing longitudinally from between the beaks. Seeds 5 to numerous, 0.8–1.2 mm long, narrowly obovoid, somewhat angular, the surface appearing smooth (microscopically pebbled), black, shiny. 2n=14. April–June.

Uncommon in the eastern half of the state, mostly in the Ozark and Ozark Border Divisions (eastern U.S. west to Minnesota and Arkansas; Canada). Shaded ledges of north-facing dolomite or sandstone bluffs and rocky slopes in mesic upland forests.

Both the generic name Mitella and the common name mitrewort refer to the dehiscing fruits, which take on the appearance of a bishop’s cap (mitre). Although the flowers are often oriented toward the side in the inflorescence, by fruiting they have moved to a position facing upward. The seeds are held in the cuplike basal portion following dehiscence and apparently are dispersed by water droplets striking the fruit during rainfall (Spongberg, 1972). The stiff lacy petals with obliquely ascending linear lobes of this beautiful little wildflower are unique among Missouri plants in their pattern of dissection.