Stephanomeria thurberi

A. Gray

Pl. Nov. Thurb., 325. 1854.

Common names: Thurber’s wirelettuce skeletonplant
Treatment appears in FNA Volume 19. Treatment on page 358. Mentioned on page 351, 352.

Perennials, 20–50 cm (rhizomes slender). Stems single, branches on distal 1/3–1/2, glabrous or sparsely puberulent. Leaves green at flowering (at least on plants of spring and early summer, frequently absent in plants of late summer); basal blades oblanceolate to spatulate, runcinate, 4–7 cm, margins pinnately lobed (faces glabrous or sparsely puberulent); cauline reduced, scalelike on plants of spring and early summer, linear and threadlike (to 3 cm) on plants of late summer. Heads borne singly on branch tips. Peduncles mostly 5–100+ mm (bracteolate). Calyculi of (4–6) appressed bractlets (unequal, lengths to 1/2 phyllaries). Involucres 9–11 (–12) mm (phyllaries 6–8, glabrous). Florets 10–16 (–20). Cypselae tan, 5–6 mm, faces smooth, grooved; pappi of 30–40, white bristles (persistent), wholly plumose. 2n = 16.


Phenology: Flowering May–Sep.
Habitat: Open, sandy sites in juniper-mesquite grasslands and in yellow pine forests, sometimes growing as weed along roadsides
Elevation: 1200–2500 m

Distribution

V19-566-distribution-map.gif

Ariz., N.Mex., Tex., Mexico (Sonora)

Discussion

Stephanomeria thurberi has been collected most often in May, June, and early July. These specimens have well developed basal rosettes, stems with nodes 3+ cm apart, relatively short branches, usually only on the distal 30–50%, and scalelike, cauline leaves. That is the form described by Gray. Another form has been collected from late July into early September that is morphologically distinct, as first pointed out by A. S. Tomb on the labels of specimens he collected in 1968 and 1970 (see below). That “summer form” lacks basal rosettes, the stems have more numerous nodes, about 1 per cm, beginning at ground level, and threadlike cauline leaves 3–4 cm. Those specimens usually have relatively few heads. Some specimens collected in July are intermediate, having basal rosettes and relatively long, threadlike cauline leaves, or no rosettes and relatively short, scalelike cauline leaves.

It is not known if the different growth forms represent distinct genotypes that initiate growth at different times, or if the same individual produces aboveground parts with differing appearances during the growth season. It is also not known if the two forms commonly grow together as they do in Coconino County, Arizona (Tomb 280, August 10, 1968, and Tomb 631, June 12, 1970), or if they generally occupy different habitats. The unusual situation calls for study.

Selected References

None.

Lower Taxa

None.

"fine" is not a number.

... more about "Stephanomeria thurberi"
rounded;acute +
scarious +
ovate +  and lanceolate +
paniculiform +  and corymbiform +
indeterminate +  and determinate +
L. D. Gottlieb +
A. Gray +
runcinate +, oblanceolate +  and spatulate +
4 cm40 mm <br />0.04 m <br /> (7 cm70 mm <br />0.07 m <br />) +
decurrent +
compound +  and simple +
runcinate;linear;oblong oblanceolate or spatulate +
tuberculate +, rugose +, muricate +  and smooth +
puberulent +  and glabrous +
filiform +
thread-like +  and scale-like +
Thurber’s wirelettuce +  and skeletonplant +
zygomorphic +, actinomorphic +  and (3-)5-merous +
white +, lavender +  and pink +
5-angled +  and columnar +
Ariz. +, N.Mex. +, Tex. +  and Mexico (Sonora) +
1200–2500 m +
bumpy +  and tuberculate +
winged +  and beaked +
dispersed +
Open, sandy sites in juniper-mesquite grasslands and in yellow pine forests, sometimes growing as weed along roadsides +
indeterminate +
each +  and sessile +
1.1 cm11 mm <br />0.011 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
less cylindric;turbinate +
0.9 cm9 mm <br />0.009 m <br /> (1.1 cm11 mm <br />0.011 m <br />) +
cauline +  and basal +
2-carpellate +
white +  and tan +
persistent +
connate +  and distinct +
0.5 cm5 mm <br />0.005 m <br /> (10 cm100 mm <br />0.1 m <br />) +
Flowering May–Sep. +
connate +  and distinct +
5 +  and 12 +
subequal +  and unequal +
Pl. Nov. Thurb., +
flat;convex +
slender +  and stout +
exalbuminous +
branched +  and simple +
1 (?) +  and 8 (?) +
hairy +  and glabrous +
appendaged +  and truncate +
papillate +
Undefined tribe Lactuceae +
Stephanomeria thurberi +
Stephanomeria +
species +
20 cm200 mm <br />0.2 m <br /> (50 cm500 mm <br />0.5 m <br />) +
shrub +  and subshrub +