Euphorbia ouachitana

Mayfield

J. Bot. Res. Inst. Texas 7: 642, figs. 2[row 2, right], 6. 2013.

Endemic
Treatment appears in FNA Volume 12. Treatment on page 306. Mentioned on page 297.

Herbs, annual, with taproot. Stems erect-ascending, often basally decumbent, often branched near base, 12–28 cm, glabrous. Leaves: petiole 0–3 mm; blade broadly oblanceolate to subspatulate, or proximalmost often orbiculate, 3–20 × 3–9 mm, base attenuate, margins entire, apex rounded to emarginate, surfaces glabrous; venation pinnate, midvein prominent. Cyathial arrangement: terminal pleiochasial branches 3, 1–3 times 2-branched; pleiochasial bracts ovate-deltate to subrhombic-ovate, shorter and wider than distal leaves; dichasial bracts connate 1/4 length, not imbricate, broadly deltate to subreniform, base truncate to broadly obtuse, margins entire, apex obtuse to bluntly acuminate; axillary cymose branches 1–5. Cyathia: peduncle 0.4–0.7 mm. Involucre infundibular, 1.3–1.6 × 1–1.2 mm, glabrous; glands 4, crescent-shaped; 0.4–0.5 × 0.8–1 mm; horns divergent, 0.2–0.4 mm. Staminate flowers 15–20. Pistillate flowers: ovary glabrous; styles 0.8 mm, 2-fid. Capsules ovoid-globose, 2.6–2.7 × 2.5–2.7 mm, slightly lobed; cocci rounded to ± flattened, smooth, glabrous; columella 2–2.1 mm. Seeds dark-brown, oblong-ovoid, 1.5–2 × 1–1.6 mm, with deep, rounded pits in 3–4 regular vertical rows; caruncle reniform-ovate, conic, 0.5–0.7 × 0.5–0.8 mm. 2n = 26.


Phenology: Flowering and fruiting spring.
Habitat: Semiopen forests, bluffs and ledges, stream banks, glades.
Elevation: 100–400 m.

Distribution

V12 571-distribution-map.jpg

Ark., Mo., Okla., Tenn., Tex.

Discussion

Euphorbia ouachitana is restricted to semiopen forests and woodlands in the south-central United States. It is similar to E. commutata and has been most commonly identified as that species in the past. However, it differs in its consistently brown seeds that have pits in regular, vertical rows. The two species also differ in E. commutata’s numerous, proximal, long-petiolate elliptic leaves. The proximal leaves of E. ouachitana are spatulate with an orbiculate blade and petiolelike base. Aside from the restricted distribution of E. ouachitana in Missouri and Tennessee, the ranges of E. ouachitana and E. commutata do not overlap (see M. H. Mayfield 2013 for a detailed discussion of the distribution). Euphorbia ouachitana is most common in the Ouachita Mountains from southeastern Oklahoma to Hot Springs County, Arkansas.

Selected References

None.

Lower Taxa

None.

"/4" is not declared as a valid unit of measurement for this property."shorter and wider" is not a number."connate" is not a number. "distinct" is not a number."connate" is not a number. "distinct" is not a number.

... more about "Euphorbia ouachitana"
obtuse;bluntly acuminate +
Ricarda Riina +, Dmitry V. Geltman +, Jess A. Peirson +  and Paul E. Berry +
Mayfield +
truncate +  and broadly obtuse +
broadly oblanceolate;subspatulate +
dichasial +  and pleiochasial +
not imbricate +
broadly deltate +  and subreniform +
cymose +, branched +, unbranched +  and pleiochasial +
arranged +  and opposite +
additional;2;4 +
0.26 cm2.6 mm <br />0.0026 m <br /> (0.27 cm2.7 mm <br />0.0027 m <br />) +
lobed +  and ovoid-globose +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.27 cm2.7 mm <br />0.0027 m <br />) +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.07 cm0.7 mm <br />7.0e-4 m <br />) +
conic +  and reniform-ovate +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.08 cm0.8 mm <br />8.0e-4 m <br />) +
rounded +  and more or less flattened +
0.2 cm2 mm <br />0.002 m <br /> (0.21 cm2.1 mm <br />0.0021 m <br />) +
Ark. +, Mo. +, Okla. +, Tenn. +  and Tex. +
100–400 m. +
pistillate +  and staminate +
0.4mm;0.5mm +
subtending +
crescent--shaped +
0.8mm +  and 1mm +
Semiopen forests, bluffs and ledges, stream banks, glades. +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.04 cm0.4 mm <br />4.0e-4 m <br />) +
axillary +  and terminal +
0.13 cm1.3 mm <br />0.0013 m <br /> (0.16 cm1.6 mm <br />0.0016 m <br />) +
infundibular +
0.1 cm1 mm <br />0.001 m <br /> (0.12 cm1.2 mm <br />0.0012 m <br />) +
caducous +, deciduous +  and persistent +
bractlike +
palmate +  and pinnate +
toothed +  and entire +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.07 cm0.7 mm <br />7.0e-4 m <br />) +
connate;distinct +
hairy +  and glabrous +
0 cm0 mm <br />0 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
Flowering and fruiting spring. +
rounded +
J. Bot. Res. Inst. Texas +
3 +  and 4 +
dark-brown +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
oblong-ovoid +
0.1 cm1 mm <br />0.001 m <br /> (0.16 cm1.6 mm <br />0.0016 m <br />) +
free +, connate +  and distinct +
erect-ascending +
12 cm120 mm <br />0.12 m <br /> (28 cm280 mm <br />0.28 m <br />) +
herbaceous +  and woody +
deciduous +  and persistent +
connate +  and distinct +
0.8 cm8 mm <br />0.008 m <br /> (?) +
Galarhoeus +  and Tithymalus +
Euphorbia ouachitana +
Euphorbia subg. Esula +
species +
1-3 times 2-branched +  and pleiochasial +
rounded +  and attenuate +
10 +, 9 +, 8 +, 7 +  and 6 +