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Volume IV (1988) - Flora of New Zealand Naturalised Pteridophytes, Gymnosperms, Dicotyledons
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Cirsium Mill.

CIRSIUM Miller

Biennial or perennial herbs, rarely annual. Stems winged or not. Hairs bristly, or soft and multicellular, or cobwebby. Lvs alternate, sessile, entire or pinnatifid or pinnatisect, dentate; lobes and teeth spine-tipped. Capitula homogamous, cylindric, ovoid or globose, solitary or in corymbs or clusters. Involucral bracts in several series, deltoid, lanceolate or linear; hairs cobwebby or 0; outer bracts usually spine-tipped, often spreading. Receptacle flat; scales numerous, setaceous. Florets ⚥ or unisexual, all tubular. Corolla glabrous, 5-lobed, usually purple, sometimes white or yellow. Anthers acute at apex, with basal appendages 0.5-1.5 mm long; filaments ciliate. Style branches linear, erect, appressed. Achenes obovoid, weakly flattened, glabrous, smooth; achene insertion basal; pappus hairs in several rows, soft, silvery, plumose, united at base into a ring.

Key

1
Capitula cylindric to narrowly ovoid at flowering, < 2.5 × 2 cm; apex of outer involucral bracts erect or suberect, with weak spine 1-(2) mm long; corolla < 20 mm long; cilia on pappus bristles < 3 mm long
2
Capitula ovoid, waisted at flowering, > 2.5 × 2.5 cm; apex of outer involucral bracts suberect to patent or recurved, with strong spine 3-4-(6) mm long; corolla > (18)-20 mm long; cilia on pappus bristles mostly > 3 mm long
3
2
Perennial with creeping rhizomes; stem glabrous, at least above, or with sparse cobwebby hairs between ribs, not winged or with short wing 0-1-(2) cm long decurrent from lf base; pappus 20-25 mm long (shorter on ♂ florets)
1. *arvense
Biennial with fibrous roots; stem with soft scattered multicellular and fine cobwebby hairs, winged between lf bases; pappus 8-12 mm long
3. *palustre
3
Stems not winged; lamina with sparse soft multicellular hairs above; corolla 18-25 mm long; stigma not, or barely, exserted beyond corolla lobes
2. *brevistylum
Stems winged; lamina with short stiff pale spinous bristles above; corolla 28-33 mm long; stigma exserted c. 3 mm beyond corolla lobes
4. *vulgare

150 spp., N. temperate. Naturalised spp. 4.

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