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Published In: Species Plantarum 2: 979. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced

 

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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.

 
 


 

 
 
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