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.

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 />) +