13. Chenopodium opulifolium Schrad. ex W.D.J. Koch & Ziz
Pl. 356 c–e; Map
1533
Plants annual,
without an odor. Stems 20–100 cm long, erect or ascending, unbranched or more
commonly few- to much-branched above the base, glabrous or sparsely
white-mealy, often somewhat reddish-tinged or reddish-striped. Leaves sessile
to more commonly short-petiolate. Leaf blades 1–4 cm long, mostly 1.0–2.5 times
as long as wide (1–3 cm wide), ovate to ovate-triangular or rhombic, bluntly to
sharply pointed at the tip, angled to nearly truncate at the base, usually with
a pair of triangular lobes below the midpoint, green to grayish green,
relatively thin and herbaceous in texture, the margins otherwise entire or wavy
to irregularly several-toothed, the upper surface glabrous or nearly so, the
undersurface sparsely to densely white-mealy. Venation noticeably branched,
with usually 3 main veins. Inflorescences axillary and terminal, consisting of
short spikes with small clusters of flowers, the terminal ones usually grouped
into small to relatively large panicles. Flowers not all maturing at the same
time. Calyx 5-lobed to about the midpoint, the fused portion extending beyond
the rim of the fruit, covering the entire fruit except sometimes for a minute
area surrounding the style, the lobes 0.5–0.8 mm long, broadly ovate, rounded
or bluntly pointed at the tip, broadly keeled and often appearing somewhat
pouched dorsally, moderately to densely white-mealy. Stamens 5. Stigmas 2.
Fruits 1.0–1.4 mm wide, depressed-ovoid, the seeds positioned horizontally, the
wall thin, membranous, and somewhat translucent, smooth, difficult to separate
from the seed or less commonly easily separable. Seeds black, shiny, smooth at
maturity, rounded along the rim. 2n=54. July–November.
Introduced,
uncommon, known thus far only from Jackson and Jasper Counties and the city of
St. Louis (native of Europe, Asia; introduced sporadically in the U.S. and Canada).
Railroads and open, disturbed areas.
This species was
first reported for Missouri by Mühlenbach (1979). The determination of Missouri
materials is somewhat controversial. Sergei Mosyakin of the Institute of Botany
in Kiev, Ukraine, who has been studying North American populations of the C.
album complex, has annotated some of the Missouri materials as C. Hborbasii
Murr, a fertile putative hybrid between C. album and C. opulifolium.
DvoÍák (1991) documented the subtle morphological variation in the complex,
noting that various populations of the hybrid could only be distinguished from
one or the other parent by careful measurement of quantitative features
involving pollen grains and/or leaf blade dimensions and lobing patterns.