Stylocline in Flora of North America @ efloras.org

99. Stylocline Nuttall, Trans. Amer. Philos. Soc., n. s. 7: 338. 1840.

Neststraw [Greek stylos, column, pillar, or pole, and cline, couch or bed (or gyne, female, specified by Nuttall in protologue), alluding to narrowly cylindric receptacles of the type species]

James D. Morefield

Annuals, 1–10(–20) cm. Stems 1, ± erect, or 2–10+, ascending to ± prostrate. Leaves cauline; mostly alternate; blades oblanceolate to lanceolate or broader. Heads in glomerules of 2–10 (rarely borne singly) in ± dichasiform (sometimes ± paniculiform) arrays. Involucres 0 or inconspicuous. Phyllaries 0, vestigial, or 1–4, unequal or subequal (similar to paleae). Receptacles cylindric to clavate (heights 2.8–8 times diams.), glabrous. Pistillate paleae falling, erect to ascending; bodies with 5+ nerves (nerves ± parallel, obscure), ± ovate or boat-shaped, saccate most of lengths (obcompressed to terete, not galeate, each usually enclosing a floret, outermost open in 2 spp.); wings ± erect (apical). Staminate paleae readily falling, mostly 2–4, erect in fruit (not enlarged), shorter than pistillate paleae; bodies linear-lanceolate to oblanceolate. Pistillate florets 12–25+. Functionally staminate florets 2–6; corolla lobes (4–)5, ± equal. Bisexual florets 0. Cypselae brown, monomorphic: compressed to obcompressed, ± obovoid, slightly incurved, abaxially gibbous, faces glabrous, smooth, shiny; corolla scars subapical; pappi: pistillate 0, staminate rarely 0, usually of 1–10(–13) bristles (hidden in heads). x = 14.

Species 7 (7 in the flora): sw United States, nw Mexico.

See discussion of Filagininae following the tribal description (p. 385).

Stylocline occurs in Mediterranean, desert, and semi-desert climates; most species appear only after exceptionally wet winters, or in moisture-accumulating microsites (e.g., rock bases, washes, shrub drip-lines). Plants usually grow in undisturbed soils (often with soil crusts) and sometimes colonize stabilized disturbances.

In some species of Stylocline, the outermost bracts of heads are merely concave, not saccate; these are paleae (if they subtend and fall with florets) or phyllaries (if they persist and subtend only adjacent saccate paleae). Texture of the palea bodies is diagnostic for each species. In dried specimens, chartaceous bodies tear easily and irregularly when the abaxial indument is gently scraped. Cartilaginous bodies can be scraped clean without tearing and split lengthwise only if forced.

Stylocline appears to be ancestral to Micropus and Psilocarphus, and derived from, sister to, and/or reticulate with Logfia (J. D. Morefield 1992). Stylocline citroleum, S. sonorensis, and L. depressa show some transitional traits between the genera.

SELECTED REFERENCE

Morefield, J. D. 1992. Evolution and Systematics of Stylocline (Asteraceae: Inuleae). Ph.D. dissertation. Claremont Graduate School. California.

1 Longest pistillate paleae winged proximally and distally, wings widest in proximal ²/3 of palea lengths; phyllaries ± persistent, elliptic or broader, 1–3.5 mm (2)

+ Longest pistillate paleae winged distally, wings widest in distal ¹/3 of palea lengths; phyllaries 0, vestigial, or falling, ± subulate, mostly 0.1–0.5 mm (3)

2 (1) Longest pistillate paleae: wings broadly ovate (bases rounded or cordate); staminate ovaries vestigial, 0–0.2 mm, pappi usually of 1–5 bristles; heads arachnoid to thinly lanuginose (often shiny, indument obscured by palea wings) 1 Stylocline gnaphaloides

+ Longest pistillate paleae: wings elliptic to slightly obovate (bases acute); staminate ovaries partially developed, (0.2–)0.3–0.6 mm, pappi of (5–)6–12(–13) bristles; heads thickly lanuginose (dull, indument evident) 2 Stylocline citroleum

3 (1) Receptacles clavate, heights 2.8–3.5 times diams.; staminate ovaries partially developed, 0.3–0.6 mm (cypselae 0.6–0.8 mm; heads ± spheric, diams. 3–4 mm; longest pistillate paleae 1.9–3.1 mm; proximal leaves blunt) 3 Stylocline sonorensis

+ Receptacles ± cylindric, heights 4–8 times diams.; staminate ovaries ± vestigial, 0–0.3(–0.4) mm (cypselae 0.8–1.6 mm, heads ovoid to ellipsoid or diams. 5–9 mm, longest pistillate paleae 3.4–4.5 mm and/or proximal leaves acute) (4)

4 (3) Heads ± spheric, thickly lanuginose, largest diams. 5–9 mm; pistillate paleae: longest 3.4–4.5 mm, outermost saccate (5)

+ Heads ovoid to ellipsoid, thinly lanuginose, largest diams. 1.5–4 mm; pistillate paleae: longest 2–3.3 mm, outermost open, concave (6)

5 (4) Bodies of longest pistillate paleae (except midnerves) chartaceous; cypselae compressed; largest capitular leaves (some or all) subulate to lanceolate (widest in proximal ¹/3), (7–)11–17 mm (distalmost mainly 1.5–2 times head heights) 4 Stylocline micropoides

+ Bodies of longest pistillate paleae cartilaginous; cypselae obcompressed; largest capitular leaves (all) ± elliptic to ± oblanceolate (widest in distal ²/3), 4–11 mm (distalmost mainly 0.8–1.2 times head heights) 5 Stylocline intertexta

6 (4) Heads 2.5–4 mm diam.; longest pistillate paleae 2.8–3.3 mm; cypselae 1.1–1.6 mm; staminate corollas 1.1–1.7 mm (lobes usually 5); leaves ± acute 6 Stylocline psilocarphoides

+ Heads 1.5–2.5 mm diam.; longest pistillate paleae 2–2.7 mm; cypselae 0.7–1 mm; staminate corollas 0.8–1.1 mm (lobes usually 4); leaves blunt 7 Stylocline masonii

Lower Taxa