Sisymbrium irio
Sisymbrium linifolium
London hedge-mustard, London rocket
flax-leaf plains mustard, flax-leaf tumble-mustard, lava cress, plains mustard, rush mustard, Salmon River plainsmustard
erect, branched proximally and distally, (1–)2–6(–7.5) dm, glabrous or sparsely pubescent at least basally.
erect or ascending, unbranched or branched (few) distally, (1.5–)3–7(–11) dm, glabrous distally.
not rosulate;
petiole (0.5–)1–4.5(–6) cm;
blade oblanceolate or oblong (in outline), (1.5–)3–12(–15) cm × (5–)10–60(–90) mm, margins runcinate to pinnatisect;
lobes (1–)2–6(–8) on each side, oblong or lanceolate, smaller than terminal lobe, margins entire, dentate, or lobed.
(soon withered);
not rosulate;
petiole (proximally) (0.5–)1–3 cm;
blade similar to proximal cauline, 1.5–6 cm, margins entire, pinnatifid or pinnatisect;
lateral lobes oblong to linear, 0.5–2.5 cm × 0.3–1(–2) mm, margins entire.
similar to basal; (distalmost) blade (smaller, to 2 cm wide), margins entire or 1–3-lobed.
sessile or shortly petiolate;
blade usually filiform to linear, rarely oblanceolate, 1–2.5–9(–12) cm × 1–3.5(–5) mm (smaller distally, base attenuate or cuneate), margins usually entire, rarely dentate or pinnately lobed.
sepals erect, oblong, 2–2.5 × 1–1.5 mm;
petals oblong-oblanceolate, 2.5–3.5(–4) × 1–1.5 mm, claw 1–1.5 mm;
filaments 2.5–4 mm;
anthers ovate, 0.5–0.9 mm.
sepals ascending, oblong to oblong-linear, (3–)4–7 × (0.8–)12 mm;
petals spatulate, (6–)8–12 × (1.5–)2–4 mm, claw 2–5 mm;
filaments (yellowish), (4–)5–7 mm;
anthers linear, 1.5–2.5mm.
divaricate or ascending, slender, much narrower than fruit, (5–)7–12(–20) mm.
divaricate to ascending, slender, narrower than fruit, (3–)5–9(–11) mm.
(divaricate to ascending, young fruits overtopping flowers), narrowly linear, straight or slightly curved inward, slightly torulose, slender, (2.5–)3–4(–5) cm × 0.9–1.1 mm;
valves glabrous;
ovules 40–90 per ovary;
style 0.2–0.5 mm;
stigma prominently 2-lobed.
(divaricate to erect), narrowly linear, smooth, slender, (2.5–)3.5–6.5 cm × 0.9–1.2 mm;
valves glabrous;
ovules 60–94 per ovary;
style 0.5–1 mm;
stigma prominently 2-lobed.
0.8–1 × 0.5–0.6 mm.
1–2 × 0.4–0.6 mm.
= 14.
= 14.
Sisymbrium irio
Sisymbrium linifolium
N. H. Holmgren (2005b) recognized Sisymbrium linifolium and others (see 86. Hesperidanthus) in Schoenocrambe even though the molecular evidence (S. I. Warwick et al. 2002) overwhelmingly shows that the latter is nested within Sisymbrium, whereas the species of Hesperidanthus are not closely related. Indeed, I. A. Al-Shehbaz et al. (2006) placed Hesperidanthus and Sisymbrium in different tribes. This is an example where the superficial resemblances in fruit morphology are the result of convergence and can easily mislead to erroneous taxonomy.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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