Acanthospermum

Schrank

Pl. Rar. Hort. Monac. 2: plate 53. 1820.

Etymology: Greek acantha, prickle, and sperma, seed, alluding to prickly “fruits”
Treatment appears in FNA Volume 21. Treatment on page 36. Mentioned on page 33.
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 TaxonIllustrator 
FNA21 P07 Acanthospermum austral.jpegAcanthospermum australe
Polymnia canadensis
Guizotia abyssinica
Barbara Alongi
Linda Ann Vorobik
Yevonn Wilson-Ramsey

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 glanddotted. 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.

Distribution

Introduced; mostly tropical to warm-temperate New World, also in Old World

Discussion

Species 6 (3 in the flora).

Key

1 Fruits 7–9+ mm, 5–7-ribbed, terminal spines 0 Acanthospermum australe
1 Fruits 2–6 mm, 3-ribbed or not notably ribbed, terminal spines 2 > 2
2 Leaf blades rhombic-ovate to obovate, (20–)40–120(–150+) mm; fruits not notably ribbed, prickles ± scattered Acanthospermum hispidum
2 Leaf blades ovate to lyrate, 10–30(–45) mm; fruits usually 3-ribbed, prickles mostly along 2 ribs and around apices Acanthospermum humile
... more about "Acanthospermum"
not tailed +, rounded +  and obtuse +
connate +  and distinct +
subequal +
scarious +
usually ovate +  and lanceolate +
usually deltate +  and lanceolate +
corymbiform +  and open +
indeterminate +  and determinate +
John L. Strother +
Schrank +
decurrent +
compound +  and simple +
lyrate;mostly elliptic;deltate rhombic or ovate +
winged;ribbed;winged;ribbed +
tuberculate +  and rugose +
barbellulate +  and barbellate +
obovoid +  and more or less prismatic +
fertile +  and bisexual +
mostly tropical to warm-temperate New World +  and also in Old World +
Greek acantha, prickle, and sperma, seed, alluding to prickly “fruits” +
glabrescent +, glabrate +, usually pilosulous +  and sericeous +
scabrellous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
in open , corymbiform arrays +  and singly +
indeterminate +
homogamous +  and heterogamous +
each +  and sessile +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
hemispheric +
sessile +  and petiolate +
deltate +
dentate to pinnatifid or palmatifid +  and entire +
2-carpellate +
persistent +
rudimentary +
10 +  and 13 +
Pl. Rar. Hort. Monac. +
bearing subulate enations +, hairy +  and bristly +
blake1921a +
exalbuminous +
erect +  and more or less prostrate +
appendaged +  and truncate +
hirsutulous +  and glabrous +
papillate +
Compositae +
Acanthospermum +
Asteraceae (tribe Heliantheae) subtribe Melampodiinae +
campanulate +
toothed +  and entire +
60 cm600 mm <br />0.6 m <br /> (120 cm1,200 mm <br />1.2 m <br />) +
10 cm100 mm <br />0.1 m <br /> (60 cm600 mm <br />0.6 m <br />) +