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Published In: Journal of the Arnold Arboretum 29(2): 193. 1948. (J. Arnold Arbor.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/4/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced

 

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2. Amaranthus arenicola I.M. Johnst. (sandhills pigweed, sandhills amaranth)

Pl. 197 e, f; Map 811

Plants dioecious. Stems 50–200 cm long, erect or ascending, glabrous or nearly so, unarmed. Leaves mostly long-petiolate. Leaf blades 1–8 cm long, narrowly oblong-lanceolate to oblong-elliptic, narrowed or tapered to a bluntly or sharply pointed tip, narrowed or tapered at the base, glabrous. Inflorescences dull or grayish green, occasionally dull reddish-tinged, mostly terminal, the axillary inflorescences mostly elongate spikes, the terminal inflorescence a panicle with few to numerous ascending branches, the flowers often grouped into discontinuous clusters or regions along the basal portions of the spikes, the tip usually straight or nearly so at maturity, the main axis and branches glabrous or nearly so. Bracts 1.5–2.5 mm long, shorter than (in staminate plants) to about as long as (in pistillate plants) the sepals, lanceolate to narrowly ovate, narrowed or tapered to a sharply pointed tip, with a somewhat thickened green midrib and relatively broad, thin, papery margins, the midrib not or only slightly extending beyond the main body as a minute, sharp point. Staminate flowers with 5 more or less similar sepals, these 3–5 mm long, erect or very slightly outward-curved, lanceolate to oblong-elliptic, narrowed to a minute, sharp point at the tip, the inner ones otherwise bluntly pointed to shallowly and minutely notched, the outer ones bluntly to sharply pointed. Stamens 5. Pistillate flowers with 5 sepals, these outward-curved at the tip, oblanceolate to spatulate, rounded or bluntly pointed at the tip, the midrib not or only slightly extending beyond the main body as a minute, sharp point, the inner ones 1.5–2.0 mm long, the outer ones 2.0–2.5 mm long, bluntly pointed at the tip. Stigmas 2(3), spreading. Fruits 1.4–1.7 mm long, circumscissilely dehiscent at about the midpoint, the surface smooth when dry. Seeds 1.0–1.3 mm in diameter, rounded along the rim, the surface reddish brown to black. 2n=32. June–October.

Introduced, known only from the St. Louis and Kansas City metropolitan areas (native of Iowa to Wyoming south to Texas and New Mexico; introduced eastward to Virginia and New Jersey and westward to California). Railroads and open, sandy, disturbed areas.

The name A. torreyi (A. Gray) Benth. ex S. Watson, used for this species by most earlier authors (Steyermark, 1963), was originally described based on a mixture of specimens now referred to several western Amaranthus species and long misapplied to A. arenicola (Sauer, 1955).

 
 


 

 
 
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