Perennial (or possibly sometimes annual) herb to 1.8 m. tall from a thick tap-root; stems strict and sparsely branched, often streaked with purple above.. Leaves narrow and elongate; radical leaves oblanceolate, up to ± 30 cm. long, 3.5 cm. wide, narrowly acute at the apex, strongly attenuated at the base so as to appear long-petiolate; cauline leaves lanceolate to oblong-lanceolate, 4–20 cm. long, 0.7–2 cm. wide, the uppermost sessile, the lower gradually more attenuate until similar to radicals; both surfaces sparsely to fairly densely covered with white hairs arising from cystolith spots.. Flowers in long-pedunculate well-branched compound dichasia of scorpioid cymes which in the early stages are ± capitate and distinctive; cymes ultimately ±12 cm. long; peduncles up to 16 cm. long; pedicels 1.5–3 mm. long; all axes densely white pubescent.. Calyx-lobes oblong-elliptic, 2–3 mm. long, ± 1 mm. wide, distinctly ciliolate, pubescent outside with hairs from tubercular cystolith bases, very distinct near base.. Corolla deep blue, white at throat, rarely all white; tube 2.5–3.5 mm. long; lobes ± round, 2–4 mm. long and wide; style (1.3–) 1.8 mm. long to over 2 mm. long in fruit, slender.. Nutlets greyish, ovate in plan, 2–2.2 mm. long, 1.8–2 mm. wide, with short triangular glochidia on the back and around the margin and 2 or 3 across the median ridge, also a few shorter ones between.. Fig. 33/1–4, p. 116.
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