Euphorbia roemeriana

Scheele

Linnaea 22: 151. 1849.

Common names: Roemer’s spurge
Endemic
Synonyms: Tithymalus roemerianus (Scheele) Small
Treatment appears in FNA Volume 12. Treatment on page 308. Mentioned on page 297.

Herbs, annual, with taproot. Stems erect, occasionally decumbent at base, branched, 15–30 cm, glabrous. Leaves: petiole 2–5 mm; blade oblanceolate to obovate, 5–20 × 5–10 mm (larger leaves in distal portion of stem), base cuneate to attenuate, margins entire, apex rounded, surfaces glabrous; venation pinnate. Cyathial arrangement: terminal pleiochasial branches 3, 1–4 times 2-branched; pleiochasial bracts ovate to oblong, similar in size to distal leaves; dichasial bracts connate 1/2 length, reniform to semicircular, base truncate to perfoliate, margins entire, apex rounded to obtuse; axillary cymose branches 0–3. Cyathia: peduncle 0–0.9 mm. Involucre campanulate, 1.5–2 × 1–1.6 mm, glabrous; glands 4, elliptic to trapezoidal, 0.4–0.6 × 0.7–1.2 mm; horns slightly convergent, 0.1–0.3 mm. Staminate flowers 10–12. Pistillate flowers: ovary glabrous; styles 0.6–1 mm, 2-fid. Capsules subglobose, 2–2.5 × 2.4–3 mm, slightly lobed; cocci rounded, smooth, glabrous; columella 1.5–1.8 mm. Seeds brown, oblong-ovoid, 1.6–1.8 × 1.4–1.5 mm, with scattered, deep and broad pits; caruncle conic, reniform, 0.3–0.4 × 0.4–0.6 mm.


Phenology: Flowering and fruiting spring.
Habitat: Rich calcareous soils, creek canyons.
Elevation: 100–300 m.

Discussion

D. S. Correll and M. C. Johnston (1970) suggested that Euphorbia roemeriana, which is restricted to the eastern part of the Edwards Plateau, is the southern counterpart of E. commutata, to which it is morphologically very similar. However, molecular phylogenetic analyses indicate that it is most closely related to E. austrotexana and E. longicruris (J. A. Peirson et al. 2014). Euphorbia roemeriana can be distinguished from E. commutata and several of the other small, annual species of subg. Esula by its consistently connate dichasial bracts.

Selected References

None.

Lower Taxa

None.

"/2" is not declared as a valid unit of measurement for this property."connate" is not a number. "distinct" is not a number."connate" is not a number. "distinct" is not a number.

... more about "Euphorbia roemeriana"
rounded;obtuse +
Ricarda Riina +, Dmitry V. Geltman +, Jess A. Peirson +  and Paul E. Berry +
Scheele +
truncate;perfoliate +
cuneate +  and attenuate +
0.5 cm5 mm <br />0.005 m <br /> (2 cm20 mm <br />0.02 m <br />) +
oblanceolate;obovate +
0.5 cm5 mm <br />0.005 m <br /> (1 cm10 mm <br />0.01 m <br />) +
dichasial +  and pleiochasial +
reniform +  and semicircular +
cymose +, branched +, unbranched +  and pleiochasial +
arranged +  and opposite +
additional;2;4 +
0.2 cm2 mm <br />0.002 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
lobed +  and subglobose +
0.24 cm2.4 mm <br />0.0024 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.04 cm0.4 mm <br />4.0e-4 m <br />) +
reniform +  and conic +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.06 cm0.6 mm <br />6.0e-4 m <br />) +
rounded +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.18 cm1.8 mm <br />0.0018 m <br />) +
Roemer’s spurge +
100–300 m. +
pistillate +  and staminate +
0.4mm;0.6mm +
subtending +
elliptic +  and trapezoidal +
0.7mm +  and 1.2mm +
Rich calcareous soils, creek canyons. +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.03 cm0.3 mm <br />3.0e-4 m <br />) +
axillary +  and terminal +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
campanulate +
0.1 cm1 mm <br />0.001 m <br /> (0.16 cm1.6 mm <br />0.0016 m <br />) +
caducous +, deciduous +  and persistent +
bractlike +
palmate +  and pinnate +
toothed +  and entire +
0 cm0 mm <br />0 m <br /> (0.09 cm0.9 mm <br />9.0e-4 m <br />) +
connate;distinct +
hairy +  and glabrous +
0.2 cm2 mm <br />0.002 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
Flowering and fruiting spring. +
0.16 cm1.6 mm <br />0.0016 m <br /> (0.18 cm1.8 mm <br />0.0018 m <br />) +
oblong-ovoid +
0.14 cm1.4 mm <br />0.0014 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
free +, connate +  and distinct +
15 cm150 mm <br />0.15 m <br /> (30 cm300 mm <br />0.3 m <br />) +
herbaceous +  and woody +
deciduous +  and persistent +
connate +  and distinct +
0.06 cm0.6 mm <br />6.0e-4 m <br /> (?) +  and 0.1 cm1 mm <br />0.001 m <br /> (?) +
Tithymalus roemerianus +
Euphorbia roemeriana +
Euphorbia subg. Esula +
species +
1-4 times 2-branched +  and pleiochasial +
rounded +  and attenuate +
10 +, 9 +, 8 +, 7 +  and 6 +