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Electronic Flora of South Australia species Fact Sheet

Family: Phyllanthaceae
Micrantheum demissum

Citation: F. Muell., Victorian Nat. 7:67 (1890).

Synonymy: Allenia blackiana Ewart & Rees, Proc. R. Soc. Vic. n.s. 22, 1:8 (1909); A. blackiana Ewart & Rees var. microphylla Ewart & Rees, Proc. R. Soc. Vic. n.s. 22, 1:8 (1909); M. demissum F. Muell. var. microphyllum (Ewart & Rees)Griin., Pflanzenr. 58:25 ( 1913).

Common name: Dwarf micrantheum.

Dwarf dense shrubs 10-30 sometimes to 50 cm tall, the branches slender, with minute spreading hairs and grey-reddish aspect, arising from a woody tap root; leaves on very short petioles, arranged in 3's (rarely in 4's or 5's), lanceolate to ovate, 3-8 x 1.5-3.5 mm, flat, smooth above, often with thickened margins below and a faint midrib, pubescent with stiff long and short white hairs all over or on the margins only.

Flowers pink; male flowers 1-3, axillary, 1.5-2.5 mm long, attenuated into a short distinct pedicel about one-third or less of their length; calyx segments 4, the 2 outer ones ovate, smaller, 2 inner ones suborbicular, petaloid, at first imbricate, later rotate; stamens 4, rarely 3, inserted at the base of the 4-lobed rudimentary ovary and opposite the segments, filaments free, anthers semiglobular, c. 1 mm long, brown-red; female flowers sessile, single and/or scattered among the males, to 3 mm long; calyx segments 4, subequal, lanceolate; ovary 2-celled, tapering into 2 broad divergent stigmatic obtuse styles opposite the outer calyx segments.

Capsule ovoid-tetragonous, 6-7 mm long, 2-celled, with 1 seed in each cell, yellowish-green, glabrous to hairy; seed cylindrical, c. 3.5 x 1.5 mm, golden-brown, with a raised line down the inner face.

image of FSA2_Micrantheum_dem.jpg Micrantheum demissum habit, leaves and enlargement of branch, details of male flowers, details of female flowers and seeds.
Image source: fig 404 in Jessop J.P. & Toelken H.R. (Ed.) 1986. Flora of South Australia (4th edn).

Distribution:  S.Aust.: EP, SL, KI.

Conservation status: native

Flowering time: April — Oct., but mainly Aug. — Sept.

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

Biology: No text

Taxonomic notes: The mainland specimens have almost glabrous leaves and capsules, while specimens from Kangaroo Island and some coastal specimens from Fleurieu Peninsula have smaller leaves, with short spreading hairs like those on the capsule. Micrantheum demissum because of its 2-celled ovary and capsule (not 3-celled as is found in the2 other known species of Micrantheum), was put in a distinct genus, Allenia, by Ewart & Rees although variation in number of ovary cells is admitted in several other Euphorbiaceous genera.

Author: Not yet available

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