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.