Quercus robusta

C. H. Muller

Torreya 34: 119. 1934.

Conservation concernEndemicIllustrated
Treatment appears in FNA Volume 3.

Trees, deciduous, to 13 m. Bark brown or black, roughly furrowed. Twigs dark reddish-brown, 1.5-2.5 mm diam., densely pubescent or glabrate. Terminal buds glossy light-brown, acutely ovoid, 4-7 mm, glabrous or pubescent on apical 1/2. Leaves: petiole 5-20 mm, pubescent or glabrate. Leaf-blade acutely ovate to elliptic, widest at or proximal to middle, 55-120 × 20-50 mm, base cuneate to rounded or subcordate, margins with 6-8 teeth or shallow lobes with rounded sinuses, rarely entire, 1-10 awns, apex acute or attenuate; surfaces abaxially glabrous except for small axillary tufts of tomentum or pubescent along midrib, adaxially glabrous or persistently pubescent near base and along midrib. Acorns biennial; cup deeply cupshaped, 6-9 mm high × 8-12 mm wide, covering 1/4-1/3 nut, outer surface puberulent or glabrate, inner surface uniformly pubescent, scales tightly appressed, acute or attenuate; nut oblong to broadly ellipsoid, 10-22 × 7-10 mm, glabrate, scar diam. 3.5-4.5 mm.


Phenology: Flowering spring.
Habitat: Moist wooded canyons in Chisos Mountains
Elevation: 1500 m

Distribution

Loading map...
Created with Raphaël 2.2.0
V3 925-distribution-map.gif

Tex.

Discussion

Of conservation concern.

After describing this species, C. H. Muller later (1951, 1970) concluded that it represented a hybrid between Quercus emoryi and Q. gravesii. The extreme forms (e.g., the type specimens) of Q. robusta and Q. gravesii are easily differentiated, but these two taxa appear to occupy the ends of a morphologic continuum. Muller's recent view, however, is that Q. robusta deserves species status. The origin of this taxon is still worthy of study.

Selected References

None.

Lower Taxa

None.
... more about "Quercus robusta"
attenuate +  and acute +
Kevin C. Nixon +
C. H. Muller +
black;brown +
cuneate;rounded or subcordate +
2-6-lobed +
pistillate +, capitate +  and spicate +
connate +  and distinct +
starchy +  and fleshy +
tuberculate +
cup-shaped +
×8-12 +, 6mm +  and 9mm +
multibracteate +, spiny +  and scaly +
1500 m +
pistillate +  and staminate +
biennial +, annual +  and maturation +
1-seeded +  and winged +
in groups +  and enclosed +
Moist wooded canyons in Chisos Mountains +
pistillate +, spicate +  and staminate +
silky-tomentose +
5.5 cm55 mm <br />0.055 m <br /> - 12 cm120 mm <br />0.12 m <br /> +
proximal +  and middle +
acutely ovate +  and elliptic +
arranged +  and alternate +
shallow +
1 - ? +  and 10 - ? +
toothed +  and entire +
1 cm10 mm <br />0.01 m <br /> - 2.2 cm22 mm <br />0.022 m <br /> +
1/4 +  and 1/3 +
oblong +  and broadly ellipsoid +
0.7 cm7 mm <br />0.007 m <br /> - 1 cm10 mm <br />0.01 m <br /> +
glabrate +  and puberulent +
glabrate +  and pubescent +
0.5 cm5 mm <br />0.005 m <br /> - 2 cm20 mm <br />0.02 m <br /> +
Flowering spring. +
distinct +
few-to-many +
attenuate +  and acute +
reduced +
0.35 cm3.5 mm <br />0.0035 m <br /> - 0.45 cm4.5 mm <br />0.0045 m <br /> +
anastomosing +, branching +  and unbranched +
Conservation concern +, Endemic +  and Illustrated +
inconspicuous +
distinct +
linear-spatulate +
pubescent +  and glabrous +
Quercus robusta +
Quercus sect. Lobatae +
species +
pubescent +  and glabrous +
0.4 cm4 mm <br />0.004 m <br /> - 0.7 cm7 mm <br />0.007 m <br /> +
bristle-tipped +
dark reddish-brown +
0.15 cm1.5 mm <br />0.0015 m <br /> - 0.25 cm2.5 mm <br />0.0025 m <br /> +
glabrate +  and pubescent +