15.
Ambrosia chamissonis
(Lessing) Greene, Man. Bot. San Francisco. 188. 1894.
Franseria chamissonis
Lessing, Linnaea 6: 507. 1831;
F. chamissonis
subsp.
bipinnatisecta
(Lessing) Wiggins & Stockwell;
A. chamissonis
var.
bipinnatisecta
(Lessing) J. T. Howell
Perennials,
50—150(—350+) cm.
Stems
prostrate or decumbent.
Leaves
mostly alternate; petioles 15—30(—45+) mm; blades rounded-deltate to ovate or obovate, 20—45(—70+) × 10—25(—50+) mm overall, not lobed or 1—2(—3)-pinnately lobed, bases cuneate, ultimate margins entire or toothed, abaxial and adaxial faces strigillose to sericeous.
Pistillate heads
clustered, proximal to staminates; florets 1.
Staminate heads:
peduncles 0.5—2 mm; involucres shallowly cup-shaped, 4—6+ mm diam., strigillose; florets 8—25(—50).
Burs:
bodies fusiform to ± pyriform, 4—7+ mm, ± strigillose to pilosulous, spines 8—16+, scattered, stoutly conic or flattened- to triquetrous-subulate, 0.5—1.5+ mm, tips straight.
2
n
= 36.
Flowering Apr—Nov. Sandy beaches and strand; 0—10 m; B.C.; Alaska, Calif., Oreg., Wash.; Mexico (Baja California).
