Linum rupestre (A. Gray) Engelm., rock flax. Perennial herb, taprooted, several—many–stemmed at base, with spreading to ascending, usually unbranched shoots below flowering canopy, in range to 30 cm tall; shoots with only cauline leaves ascending to somewhat appressed to stem, slightly glaucous.
Stems 10–ridged, to 1.5 mm diameter, with 3 ridges descending from each leaf, tough, basal internodes short and above to 16 mm long, green and photosynthetic; solid; periderm on old stems near the ground
Leaves helically alternate ot opposite (the lowest leaves), simple, sessile, with stipules; stipules 2, at base of leaf on stem, domelike, ca. 0.3 mm long, reddish; blade linear, 7—16 × 1.2—1.4 mm, entire or sparsely short–ciliate, acuminate with short bristle at tip, 1–veined with midrib raised on lower surface and ending at tip, somewhat glaucous.
Inflorescence panicle of racemelike cymes, terminal, open, < 150 mm long, many–flowered, lateral branchlets helically alternate, bracteate but not appearing leafy; bract subtending each branchlet, leaflike, 4—5 mm long, each with 2 stipules; branchlet axes slender, wiry; bractlet subtending pedicel awl–shaped, ± 3 mm long, reddish, with 2 stipules at base, keeled with several glandular teeth along keel and margins, bristle 0.5—0.6 mm long and red–tipped; pedicel at anthesis 1.5—2 mm long increasing in fruit, somewhat flat–sided.
Flower bisexual, radial, 10—11 mm across, glabrous, open and dishlike in morning, closing before afternoon with petals readily abscising; sepals 5, helically alternate, firmly attached to receptacle, while open ascending and appressed to corolla later erect, overlapping below midpoint, unequal, outer sepals broadly lanceolate, 3—4 × 1.25 mm increasing slightly in fruit, often green to midpoint and purplish above with short bristle at tip 0.3—0.4 mm long, conspicuously 3–veined, margins and raised midvein with conspicuously glandular teeth, sepals decreasing in length outer to inner, inner sepals with wide colorless margins to bristle and green herbaceous center; petals 5, spreading, attached to base of short stamen tube, twisted in bud with overlapping limbs, short–clawed, easily dislodged; claw inverted short–deltate, pale yellowish to whitish, with tuft of short hair near base on upper surface < 1 mm from base; limb narrowly fan–shaped to oblanceolate, above hairs 8—15 × 3.4—4.7 mm, broadly rounded and weakly jagged at tip, yellow with dark faint veins radiating from base, lower surface glossy below midpoint; stamens 5, fused at their bases forming a ringlike tube around ovary base appressed to ovary, with exserted anthers touching stigmas; tube 1 mm long, pale green, with small tooth in each sinus between filaments (vestigial staminodes); filaments jto 3.3 mm long, yellow with a hint of green; anthers dorsifixed, dithecal, 0.8—1 mm long, light yellow, longitudinally dehiscent; pollen light yellow; nectaries 5, fused to stamen tube opposite filament bases; pistil 1; ovary superior, smoothly ovoid, 1.2 × 1 mm, lacking strongly 5–angled beak, green, inconspicuously striped and veined, 5–chambered becoming falsely 10–chambered by growth of false septa, with 2 ovules per chamber; styles 5, fused at based ca. 0.5 mm, erect, pale green at base to yellow above, parallel and appressed, unequal, 3.3—3.7 × 0.15 mm, exserted to level of anthers but not at same height; stigmas capitate, ± 0.3 mm across, conspicuously papillate.
Fruit capsule, schizocarpic, septicidal and loculicidal, 10–seeded, breaking into 10 crescent–shaped, 1–seeded segments, ovoid, ± 2.5 mm long + 1 mm for 5–angled beak.
Seed persistent in thick–walled fruit segment between papery divisions, ± 1.5 mm long.
A. C. Gibson