1. Axyris amaranthoides L. (Russian pigweed)
Pl. 357 e, f;
Map 1519
Plants
monoecious, annual, the taproot not tuberous-thickened. Stems 15–90 cm long,
erect or nearly so, not succulent, not appearing jointed, usually with many relatively
short, ascending branches, sparsely to densely pubescent with small, stellate
hairs. Leaves alternate, well developed, not succulent, mostly short-petiolate.
Leaf blades 2–9 cm long, elliptic or narrowly to broadly lanceolate, flattened
in cross-section, not clasping the stem, narrowed to a bluntly or sharply
pointed tip, narrowed at the base, the margins entire or shallowly and broadly
few-toothed, those of the smaller leaves sometimes curled under, the upper
surface sparsely pubescent with small, stellate hairs to nearly glabrous, the
undersurface moderately to densely pubescent with small, stellate hairs.
Inflorescences axillary and terminal, mostly panicles of short spikes
(sometimes reduced to a single short, terminal spike); the flowers not sunken
into the axis; the staminate flowers at the tips of the panicles and/or tips of
the individual pistillate spikes; the pistillate flowers in axillary clusters
and/or along the spicate panicle branches. Bracts 3 per flower, 1.5–3.5 mm
long, leaflike, lanceolate to ovate, tapered to a sharply pointed tip. Calyx of
3(4) sepals, these tiny (those of staminate flowers 0.4–0.7 mm long, those of
pistillate flowers 1.5–2.5 mm long), scalelike, irregularly oblong-ovate,
rounded at the tip, persistent at fruiting, more or less concealing the fruit,
rounded on the back, not winged, pubescent with dense, shorter, stellate, and
usually also scattered longer, unbranched hairs. Staminate flowers with the
stamens 3. Pistillate flowers with the ovary superior. Style absent or 1 and
very short, the stigmas 2, linear. Fruits 2–3 mm long, obovate or nearly
circular in outline, sometimes with a small, 2-lobed wing at the tip, flattened
vertically, indehiscent, the wall papery to membranous, usually mottled with reddish
brown spots and occasionally a few small, whitish, warty outgrowths. Seed
adhering tightly to the fruit wall, positioned vertically, 2–3 mm long, obovate
in outline, flattened, the surface smooth, brown, not or only slightly shiny,
the embryo appearing U-shaped. 2n=18. May–October.
Introduced,
uncommon, known thus far only from a historical collection from Jackson County
(northern U.S. south to Colorado and Missouri; Canada). Open, disturbed areas.