2.Oxalis dillenii Jacq. (yellow wood sorrel, gray-green wood
sorrel)
O. corniculata var. dillenii (Jacq.) Trel.
O. lyonii Pursh
Pl. 474 h–j; Map
2167
Plants
perennial, but flowering the first year and sometimes appearing annual,
initially with taproots, but usually developing blackish brown rhizomes,
lacking bulbs. Aerial stems 1 to several, 8–25 cm long, variously erect or
becoming prostrate, then not or rarely rooting at the nodes, moderately
pubescent with short, unicellular, appressed to upward-curved hairs, the
pubescence often denser near the stem tips. Leaves basal (on young plants) and
alternate, those on older stems often appearing fasciculate from the stem
nodes, the petiole moderately to densely pubescent with appressed to strongly
ascending hairs. Stipules absent or, if present, then represented by slight
thickenings or inconspicuous wings at the petiole base, these green. Leaflets
4–15(–20) mm long, obcordate, the apical notch to 1/3 of the total length, the
upper surface usually glabrous, the undersurface sparsely to moderately
pubescent with mostly appressed hairs, yellowish green to grayish green,
usually lacking purplish to brownish markings. Inflorescences umbellate with
2–5(–8) flowers, occasionally reduced to a solitary flower. Sepals 3–6 mm long,
oblong-lanceolate to narrowly oblong-elliptic, green or translucent at the tip.
Petals 5–11 mm long, yellow. Fruits 12–20(–25) mm long, cylindrical at
maturity, densely pubescent at maturity, the short, appressed to more or less
spreading, unicellular and/or multicellular hairs often hiding a layer of
microscopic hairs. Seeds 1–2 mm long, brown, the ridges grayish or whitened. 2n=18,
20, 22, 23, 24. May–November.
Scattered to
common nearly throughout the state, but apparently uncommon in northwestern
Missouri (nearly throughout the U.S.; Canada, Mexico; introduced in the
Caribbean Islands, Europe). Bottomland forests, mesic to dry upland forests,
savannas, upland prairies, glades, and banks of streams and rivers; also
pastures, fallow fields, gardens, railroads, roadsides, and disturbed areas.
Plants of O.
dillenii with prostrate stems sometimes have been misdetermined as O.
corniculata, but the noticeable stipules of that species are not present in
O. dillenii. For a discussion of problems with the separation of O.
dillenii and O. florida, see the treatment of the latter species.
Mühlenbach
(1979) reported the closely related O. texana (Small) Fedde (as O.
priceae Small ssp. texana (Small) Eiten) based on a specimen from
the St. Louis railyards. Yatskievych and Turner (1990) noted that this report
was incorrect, but mistakenly refered the specimen to O. corniculata.
The specimen has since been redetermined as O. dillenii. Oxalis
texana is endemic to portions of Arkansas, Louisiana, and Texas and differs
from O. dillenii in its usually larger number of flowers per umbel
(mostly 3–8) and larger corollas (12–16 mm long). Lourteig (1979) applied the
name O. lyonii Pursh to this taxon (which Yatskievych and Turner [1990]
followed), based on an invalid type designation; that name is better treated as
a synonym of O. dillenii (D. B. Ward, 2004).