Thamnosma texana (A. Gray) Torrey [when validly published, var. texana], texas desert–rue, dutchman’s breeches. Subshrub (suffrutescent perennial), forming shoots from ground level during earliest spring, small–leaved, several—many–stemmed at base, with ascending flowering shoots, in range to 20 cm tall; shoots with narrow, ascending cauline leaves on green (photosynthetic) stems, gland–dotted on green tissues, the glands domed from beneath the surface, when crushed producing a strong, aromatic odor like rue ( Ruta; monoterpenes), glabrous and glaucous.
Stems cylindric, of new shoot ca. 1 mm diameter, easily broken, green and glaucous, glands spaced < 0.5 mm apart, with minute dots (stomates) between glands.
Leaves helically alternate, simple, subsessile, without stipules; petiole < 0.3 mm long or somewhat enlarged at base; blade ascending to suberect, linear to narrowly oblong–linear, (5—)8—12 × 1—1.3 mm, long–tapered at base, subentire on margins (indentations associated with glands), minutely notched at tip, 1–veined with midrib slightly raised on upper surface, lower surface glaucous with margins not flat.
Inflorescence leafy cyme, terminal, at first racemelike but often forked above, 10+–flowered, bracteate, conspicuously gland–dotted, glabrous, glaucous; rachis distinctly gland–dotted; bract and bractlet close to node but not subtending pedicel, with at least 1 on opposite side of pedicel, leaflike with short petiole, oblong to linear, at anthesis 3—4 × < 1 mm increasing to 7 mm long in fruit; pedicel at anthesis 0.5—1.6 mm long, often wrinkled, increasing in thickness and conspicuously wrinkled in fruit.
Flower bisexual, radial, when ovoid 3.2—4 mm across, wider when petals spreading; calyx 4–lobed, starlike with radiating lobes, ca. 1.5 mm long; tube dishlike, ca. 0.5 mm long, yellow–green, wrinkled; lobes ± deltate, 0.7—1 mm long, with minute notch at tip, stiff and thick, sometimes tinged red on margins, glabrous, glaucous; petals 4, erect to spreading, overlapping but 1 petal interior to adjacent 2 petals, cupped–ovate, ± 4 × 3.2—3.5 mm, white to pale yellow at base and lemon yellow from below midpoint, margins yellow base–to–tip, acute to obtuse at tip, gland–dotted, midvein visible; stamens 8 in 2 close whorls, free on elevated receptacle with nectary, receptacle bumpy and light green between stamens; filaments strongly curved upward from receptacle at base, 3—3.5 mm long, white, glabrous; anthers basifixed, dithecal, 0.65—0.75 mm long, orange–yellow, longitudinally dehiscent; pollen orange–yellow; nectary part of solid, cup–shaped receptacle 1 × 1.3 mm; nectar present; pistil 1; ovary superior, strongly 2–lobed with thick lobes from midpoint and rounded at tips, ca. 1.8 × 1.6 × 1.2 mm, green and ± glossy but glaucous, gland–dotted, 2–chambered, each chamber with ca. 8 ovules attached to center; style from between lobes, ca. 1.5 mm long, light green, enlarged at base, somewhat flattened but slightly swollen below stigma; stigma terminal, at or above anthers, 2–lobed, dark green, short–hairy.
Fruit capsule, to 10–seeded, wide V–shaped with thick lobes diverged nearly 90°, lobes ca. 3 mm long and fruit ca. 7 mm across, before drying green, glaucous, and gland–dotted.
Seed kidney–shaped to D–shaped, ca. 1.5 × 1 mm, initially pale green aging whitish, conspicuously bunpy (tuberulate) on back of strongly curved embryo.
A. C. Gibson