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FNA | Family List | FNA Vol. 21 | Asteraceae

257. Acanthospermum Schrank, Pl. Rar. Hort. Monac. 2: plate 53. 1820.

[Greek acantha, prickle, and sperma, seed, alluding to prickly "fruits"]

John L. Strother

Annuals (sometimes persisting), 10–60(–120) cm. Stems erect to ± prostrate (repeatedly "forked"). Leaves cauline; opposite; petiolate or ± sessile; blades mostly elliptic to deltate, rhombic, or ovate, sometimes lyrate, ultimate margins entire or toothed, faces usually pilosulous to sericeous or scabrellous, sometimes glabrate or glabrescent, usually gland-dotted. Heads radiate, 1(–3) in "forks" of branches (terminal, appearing axillary by sympodial growth). Involucres ± hemispheric, 3–5 mm diam. (becoming ± rotate in fruit). Phyllaries persistent (outer) or falling, 10–13 in 2 series (outer 4–6 herbaceous, inner 5–8 each investing a ray ovary, enlarging in fruit to form a perigynium, shed with enclosed cypsela). Receptacles convex, paleate (paleae cuneate to spatulate, ± conduplicate or flattish, membranous). Ray florets 5–8, pistillate, fertile; corollas yellowish (tubes shorter than to equaling laminae, laminae ovate to elliptic or linear). Disc florets 3–8(–12+), functionally staminate; corollas yellowish, tubes shorter than funnelform or campanulate throats, lobes 5, deltate. Cypselae each enclosed within and shed with an often hardened, ± prickly perigynium (the ultimate "fruits" plumply ellipsoid to fusiform, or ± compressed); pappi 0 or rudimentary. x = 11.

Species 6 (3 in the flora): introduced; mostly tropical to warm-temperate New World; also introduced in Old World.


Blake, S. F. 1921. Revision of the genus Acanthospermum. Contr. U.S. Natl. Herb. 20: 383–392.

1 Fruits 7–9+ mm, 5–7-ribbed, terminal spines 0   1 Acanthospermum australe
+ Fruits 2–6 mm, 3-ribbed or not notably ribbed, terminal spines 2   (2)
2 (1) Leaf blades rhombic-ovate to obovate, (20–)40–120(–150+) mm; fruits not notably ribbed, prickles ± scattered   2 Acanthospermum hispidum
+ Leaf blades ovate to lyrate, 10–30(–45) mm; fruits usually 3-ribbed, prickles mostly along 2 ribs and around apices   3 Acanthospermum humile

Lower Taxa


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