Cirsium hydrophilum
Fl. W. Calif., 507. 1901.
Biennials or monocarpic perennials, 100–220 cm; taprooted. Stems 1–several, erect, (hollow), openly branched distally or throughout, thinly arachnoid with fine, non-septate trichomes, glabrate. Leaves: blades elliptic to broadly oblanceolate, 10–40+ cm, pinnatifid 1/2–2/3 distance to midveins, larger usually with broad sinuses, lobes broad, few lobed or dentate, main spines 2–9 mm, abaxial faces ± gray-tomentose, sometimes ± glabrate, adaxial thinly arachnoid-tomentose, soon glabrescent; basal present or withered at flowering, winged-petiolate; principal cauline sessile, progressively reduced distally, bases auriculate-clasping or shortly decurrent; distal cauline reduced, bractlike, often spinier than proximal. Heads borne singly or few at branch tips, sometimes subtended by clustered, ± leafy bracts, collectively forming ± open, many-headed paniculiform arrays. Peduncles 0–10+ cm. Involucres ovoid to campanulate, 1.5–2.5 × 1.5–3 cm, thinly arachnoid, glabrate. Phyllaries in 6–9 series, imbricate, dark green to brownish, lanceolate (outer) to linear (inner), abaxial faces with narrow glutinous ridge; outer and middle appressed, apices spreading, finely serrulate, spines slender, 1–2 mm; apices of inner erect, ± flexuous. Corollas pale rose-purple, 18–23 mm, tubes 8–10 mm, throats 5–6 mm, lobes 5–7 mm; style tips 3.5–4.5 mm. Cypselae dark-brown to black, 4–5 mm, collars very narrow, stramineous; pappi ca. 15 mm. 2n = 32.
Discussion
Varieties 2 (2 in the flora).
Selected References
None.
Key
| 1 | Heads usually 2.5–3 cm; cypselae ca. 5 mm, oblong; tidal marshes | Cirsium hydrophilum var. hydrophilum |
| 1 | Heads usually 3–3.5 cm; cypselae 4–5 mm, oblong or elliptic; serpentine springs | Cirsium hydrophilum var. vaseyi |
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