Nuytsia 8: 3 (1998) - FloraBase

Paul G. Wilson, Helipterum: Part 1
Annual erect herbs pubescent with gland-tipped septate hairs. Leaves cauline, alternate, linear.
Capitula solitary and terminal to long branches, radiant. Involucre hemispherical; bracts c. 4-seriate;
outer bracts elliptic, hyaline, long-ciliate with a brown narrow-oblong flat stereome; innermost bracts
with a narrow-elliptic hyaline long-ciliate claw, a narrow-oblong stereome, and a yellow elliptic
lamina. Receptacle minutely glandular papillose. Florets numerous, bisexual, actinomorphic.
Corolla: tube slender, glandular pilose; limb campanulate, glabrous; lobes five, ovate, vascular
strands extending to tips. Anther; appendage ovate, thin, marginal cells differentiated, basal cells ±
equilateral, medial and distal cells narrow-oblong; tails slender delicate, extending to beyond collar.
Style apex truncate; vascular strand prominent, extending almost to tip. Achene narrow-elliptic,
compressed, extending into a terminal beak, minutely papillose with 2-celled tooth-like trichomes;
carpopodium annular, short; pericarp: outer layer of 1-cell thick layer of thin-walled cubical cells;
inner layer of 2-3 rows of thick walled sclerenchymatous cells; testa extremely thin, more or less
adherent to pericarp; endosperm thin, free from testa; vascular strands of pericarp lateral (in relation
to cotyledons); vascular strand of testa passing almost completely around seed in lateral position.
Pappus bristles filiform, barbellate, united below to form a cup-shaped base, entire or slit on one side,
persistent.
Haptotrichion conicum had been placed in Waitzia since it possessed beaked achenes. It differs
from Waitzia most obviously in 1) having a different type of indumentum (not cottony), 2) having broad
flat hyaline claws to the inner involucral bracts (not terete and firm), 3) in having truncate style apices
(neither ellipsoid nor deltoid), and 4) in having delicate filamentous anther tails (not slender and firm).
Haptotrichion further differs from Waitzia in the anatomy of the achene for its pericarp has an outer
single-celled layer of thin-walled cube like cells and an inner layer of several rows of thick-walled
sclerenchymatous cells, while the testa is extremely thin and delicate. In Waitzia the pericarp consists
of a thin layer of hyaline linear cells while the testa is thick, rugose, and made up of thick-walled
collenchyma. The vascular strand in the testa of Haptotrichion passes almost completely around the
seed but in Waitzia it is confined to the base.
From Pterochaeta this genus differs in the manner of branching of the stem and inflorescence (q.v.),
in the nature of the involucral bracts, the nature of the corolla, and the nature of the anther apiculum.
In Pterochaeta, Haptotrichion and Waitzia the achenes are beaked and bear tooth-like 2-celled
trichomes but in other characters the genera are very distinct.
The genus consists of two species, both endemic to the Carnarvon District (Beard 1980) of Western
Australia.
Haptotrichion colwillii Paul G. Wilson, sp. nov. (Figure 6)
Herba erecta ad 25 cm alta. Rami glanduloso puberuli sub capitula pilosi. Folia linearia, 8-15 mm longa,
glanduloso puberula. Involucrum hemisphaericum, c. 10 mm altum et latum; bracteis exterioribus late
ellipticis, hyalinis, ciliatis; bracteis intimis ungue anguste elliptico, c. 9 mm longo, hyalino, ciliato, limbo
anguste obovato obtuso, 9-15 mm longo, luteo. Corolla c. 5 mm longa, tubo glanduloso hirtello, limbo
anguste turbinato, glabro, intra sub lobis papilloso. Achenium anguste ellipsoideum c. 2.5 mm longum,
denticulatum; rostrum gracile, laeve, ad 3 mm longum. Pappus persistens, setis in basi connatis,
tubiformibus.
Typus: 7 km S of Overlander Roadhouse [c. 170 km S of Carnarvon], Western Australia, 1 Sept. 1985,
H. Demarz 10702 (holo: PERTH).
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