Electronic Flora of South Australia
Electronic Flora of South Australia
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Electronic Flora of South Australia species Fact Sheet

Family: Orchidaceae
Acianthus caudatus

Citation: R. Br., Prod. Fl. Nov. Holl. 321 (1810).

Synonymy: Acianthus caudatus, Nemacianthus caudatus

Common name: Mayfly orchid.

Very slender, glabrous, 7-15 cm high; leaf radical or nearly so; cordate-ovate, rather thin; margins crenate or crenulate, sometimes more or less lobed; green above, reddish below, reticulate, rarely exceeding c. 2.5 cm long.

Flowers 1-6, crimson, with a musty odour, on short pedicels; dorsal sepal more or less inflexed, dilated rather narrowly over the anther, then tapering into a filiform point 2-3.5 cm long; the dilated part concave on a contracted base, 5-6 mm long; lateral sepals free, much shorter than the dorsal sepal, c. 15 mm long, tapering into fine points curving upwards at their ends; petals falcate-lanceolate, reflexed or spreading, 4-5 mm long; labellum triangular, sessile, crimson like the other parts; base erect, semi-orbicular, embracing the column; thereafter broadly but very acutely lanceolate, at first horizontal then abruptly recurved near the tip; the margins entire; lamina glandular with a smooth surface except for 2 tooth-like or triangular calli at the extreme base; column c. 4 mm long, inflexed on the summit of the ovary, almost terete in its lower two-thirds, dilated above, very narrowly winged in the terete part, widening shortly on each side of the stigma and continued upwards behind the anther; anther pointless; pollinia 2 in each cell, granular, each pair connected to a separate viscid disk in the upper border of the stigma; stigma rather prominent, hemispherical; rostellum double; each part tooth-like, bearing a relatively large viscid disk.

Published illustration: Fitzgerald (1882)Australian orchids, vol. 1, pt 7; Cady & Rotherham (1970) Australian native orchids in colour, pl. 63; Woolcock (1984) Australian terrestrial orchids, pl. 1C.

Distribution:  Forming small to extensive colonies in clay or sandy soils in open forest, sometimes colonising plantations of Pinus radiata.

S.Aust.: EP, NL, MU, YP, SL, KI, SE.   N.S.W.; Vic.; Tas.

Conservation status: native

Flowering time: Sept. — Oct.

SA Distribution Map based
on current data relating to
specimens held in the
State Herbarium of South Australia

Biology: The var. pallidus Rupp (1947), Proc. Linn. Soc. N.S.W. 71:290, has been collected in S.Aust. (SL). It differs in having yellow-green flowers with shorter segments than the type and is probably best treated as a mere colour form.

Author: Not yet available

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