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Published In: Flora Caroliniana, secundum . . . 87. 1788. (Fl. Carol.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

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

 

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1. Diodia teres Walter (rough buttonweed)

Diodella teres (Walter) Small

Pl. 545 g, h; Map 2533

Plants annual, sometimes becoming woody at the base. Stems 15–35(–80) cm long, usually erect or strongly ascending, minutely roughened and becoming more or less glabrous to sparsely or moderately pubescent with short, straight to wavy hairs of various lengths. Stipules 1–2 mm long, the bristles 5–11 on each side, variously 1–10 mm long. Leaf blades 1.0–3.5 cm long, 2–5 mm wide, narrowly lanceolate to narrowly elliptic or nearly linear, angled to somewhat rounded at the base, angled to a sharply pointed tip, the margins minutely pubescent with stiff, spinescent hairs, frequently becoming curled under (especially in plants from particularly dry microsites), the surfaces glabrous or nearly so, the venation with the midvein and usually 2 or 3 pairs of pinnate, secondary veins visible. Flowers usually solitary in the leaf axils, produced at most of the nodes. Calyces deeply 4-lobed, the lobes 1–2 mm long, triangular, often unequal. Corollas 6–7 mm long, pink to less commonly mauve or pale purple, externally glabrous or hairy, internally glabrous, the tube 4–5 mm long, the lobes 2.0–2.5 mm long, lanceolate. Styles unbranched, with a 2-lobed, capitate stigma. Fruits 3.0–3.5 mm long, 3.0–3.5 mm wide, broadly obovoid, smoothly rounded to broadly angled on the sides. 2n=28. June–October.

Scattered nearly throughout the state, but apparently absent from most of the western half of the Glaciated Plains Division (eastern U.S. to Kansas and Texas, also New Mexico, Arizona, and California; Mexico, Central America, South America, Caribbean Islands). Glades, thin-soil areas of upland prairies, sand prairies, ledges and tops of bluffs, and banks of streams and rivers; also pastures, old fields, fallow fields, old quarries and mines, railroads, roadsides, and open, disturbed areas; often in sandy or acidic soils.

As is common in annual species of weedy habit and habitat, D. teres shows considerable variation in plant size, leaf size, and pubescence, among other characters. This variation is continuous and mostly found throughout the range of the species, often within populations. Some authors have attempted to classify this variation (Fernald and Griscom, 1937), but, as was noted by Steyermark (1963), these intergrade greatly. With more collections and information on genetics now available, the five North American varieties of D. teres are now considered to represent only minor variants within a variable species, and morphological expression also is thought to be strongly influenced by the plant’s environment.

 
 


 

 
 
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