Citation: R. Br., Prod. Fl. Nov. Holl. 571 (1810).

Synonymy: S. calcaratum R. Br. var. ecorne F. Muell. ex R. Erickson & J.H. Willis, Victorian Nat. 72:133 (1956).

Common name: Book trigger-plant.

Description:
Delicate annual with an erect stem c. 8 cm tall, thread-like, little-branched, with usually 4 leaves in a basal rosette, sparsely glandular-pubescent; leaves with a petiole 0-2 mm long, obovate-spathulate to linear-oblanceolate, 2-6 x 0.5-3 mm, obtuse or rounded, flat, glabrous.

Inflorescence corymb-like with 1, rarely several, monochasia with 1-3 flowers; peduncle 1.5-7 cm long, sparsely glandular-pubescent; bracts linear-lanceolate, 1-4 mm long; sepals scarcely connate, sparsely glandular-pubescent; lobes 2-4 mm long, often unequal; corolla with a tube shorter than the sepals, with a more or less well developed spur, with 2 appendages in the throat, white or pink and with various red markings or spots on the base of the upper petal pair; lobes oblong-oblanceolate with a rounded apex on the lower pair and truncate or a variously lobed apex on the upper pair, glabrous; labellum oblong-ovate, without lobes; column with a small tooth above the corolla throat; stigma a strap-like projection between the anthers; ovary with numerous ovules on a shortly stalked spherical central placenta.

Capsule 3-5 mm diam.; seeds broadly ellipsoid, c. 0.3 mm long, with fine vertical ridges.

	Habit, flower, column and opened ovary.
Image source: fig. 640b in Jessop J.P. & Toelken H.R. (Ed.) 1986. Flora of South Australia (4th edn).

Published illustration: Erickson (1958) Triggerplants, pl. 8, figs 1-10; Cochrane el al. (1968) Flowers and plants of Victoria, fig. 121.

Distribution:  S.Aust.: EP, NL, MU, YP, SL, KI, SE.   W.Aust.; Vic. Conservation status: native Flowering time: Sept. — Nov.

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

Biology: Since considerable variation was noticed in the size of the spur at different localities it is not clear how the var. ecorne should be delimited and pending detailed investigations attention must be drawn to this extensive range of variation. Flowers without a spur can only be distinguished from the very similar S. perpusillum by the shape of the upper petals since small flowers come into range of the flowers of the latter species.

Author: Not yet available