Oxalis stricta
Oxalis macrantha
common yellow oxalis, common yellow wood sorrel, European wood-sorrel, upright yellow oxalis, upright yellow wood-sorrel, yellow woodsorrel
Price's wood-sorrel
1(–3) from base, erect or later leaning or falling over and decumbent, not rooting at nodes, 20–60(–90) cm, herbaceous, villous, hairs ± straight, spreading, usually nonseptate and septate, septate hairs commonly concentrated at nodes, very rarely only nonseptate.
usually 2–8 from base, erect initially, usually becoming decumbent, 5–20(–40) cm, becoming woody proximally, hirsute-pilose on at least proximal 2/3, hairs curved, loosely and irregularly spreading, nonseptate.
basal and cauline;
stipules rudimentary;
petiole 2–8 cm, hairs septate and nonseptate;
leaflets 3, light green to yellowish green, obcordate, (8–)10–20(–30) mm, lobed 1/5–1/3 length, surfaces glabrous, oxalate deposits absent.
basal and cauline;
stipules oblong, margins narrowly flanged or without free portions, apical auricles absent;
petiole 2–7 cm;
leaflets 3, green, obcordate, 3.5–12 mm, lobed 1/5–1/3 length, surfaces usually strigose-hirsute, sometimes glabrate, oxalate deposits absent.
usually regular cymes, rarely irregular cymes, (1–)5–7(–15)-flowered;
peduncles 3–9(–11) cm.
umbelliform cymes, less commonly irregular cymes, (1–)3–8-flowered;
peduncles (3–)5–10(–15) cm.
villous, hairs long, spreading.
homostylous or slightly to strongly heterostylous, usually within or slightly above level of leaves;
sepal apices without tubercles;
petals yellow, without red lines, (6–)8–11 mm.
distylous, well above level of leaves;
sepal apices without tubercles;
petals yellow to yellow-orange, with prominent red lines proximally, (13–)15–20(–23) mm.
± cylindric, nearly terete, abruptly tapering to apex, 8–15 mm, villous to puberulent or glabrate, hairs septate.
angular-cylindric, abruptly tapering to apex, 10–15 mm, sparsely to densely hirsute-pilose, hairs long, sometimes mostly along angles.
brown, transverse ridges rarely white.
brown, transverse ridges usually white.
= 18, 24.
Oxalis stricta
Oxalis macrantha
Oxalis stricta is uncommon and probably adventive in Canada and the western United States. The species is recognized by the combination of its tall (rarely up to nearly a meter), erect stems from a short, simple rhizome; septate hairs; cymose inflorescence; and small flowers. Septate hairs on the stems and petioles are easily recognized (lens) by their colored cross-walls, but they vary greatly in density. In villicaulis forms, the hairs are dense and evenly distributed, but in most plants over the range they are localized around the nodes and intermixed with nonseptate hairs. Often they are sparse; rarely they appear to be absent on plants with greatly reduced vestiture overall.
A. Lourteig (1979) identified this species as Oxalis fontana, typified by a plant from northern China, and applied the name O. stricta to the species identified by G. Eiten (1955, 1963) and here as O. dillenii. The basis for the difference lies in selection of lectotypes. Choice of stricta as the correct epithet acknowledges that the description of O. stricta by Linnaeus best matches these plants and that selection of a Morison illustration as lectotype characterizes the species long-naturalized and weedy in Europe and probably known first-hand by Linnaeus. C. E. Jarvis (2007) has confirmed this choice of lectotype. Oxalis dillenii is appropriately lectotypified by a John Clayton collection from Virginia. The situation has been summarized well by D. B. Ward (2004).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oxalis macrantha is restricted mostly to limestone glades in Alabama, Kentucky, and Tennessee. It is recognized by its villous to villous-hirsute stems, flowers in umbelliform cymes, and large yellow to yellow-orange corollas with red lines proximally. The lines in the throat remain visible after drying and usually can be seen on herbarium specimens even from the outside of the flower. A similar pattern also occurs in other species, especially O. grandis, O. illinoensis, and O. texana.
Seemingly disjunct plants of native habitats in Nuevo León, Mexico, identified as Oxalis macrantha apparently are more common than reported by G. L. Nesom (2009b). Whether these are actually disjunct or a parallel morphological expression derived from some Mexican species needs to be investigated.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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