Acmadenia tetragona Bartl. & H.L.Wendl.

Shrubs 0.3 to 0.6 m tall, spreading, single-stemmed at base. Branches short, fairly erect, clothed with a short erect pubescence, knotty with leaf scars. Branchlets fairly numerous, short, erect, hidden by the leaves, erect pubescent. Leaves strongly keeled, the two halves of the blade set at an angle, orbicular when pressed flat, 4.8 mm long, 4.2 mm broad, minutely pubescent, gland-dotted, ciliate, adaxially glabrous, opposite, decussate, spreading; apex trigonal obtuse; petiole very short. Inflorescence terminal, solitary, 20-25 mm diam., white with a red midrib. Bracts four, 5.5 mm long, 4 mm broad, keeled, minutely pubescent, gland-dotted, ciliate; margins broadly translucent below. Calyx lobes five, 6 mm long, 4 mm broad, keeled, sparsely pubescent and purplish above; apex obtuse, trigonal; tri-nerved, pale, glabrous and translucent below. Petals five, 3.5 mm long, 7.8 mm broad; limb spreading, orbicular, apiculate, minutely ciliate, abaxially multi-gland-dotted, narrowing below; claw about 4 mm long, narrowing towards the base, ciliate, adaxially pubescent, midrib prominent. Staminodes five, 3 mm long, 0.3 mm diam., acicular, glabrous, apex glandular. Filaments five, 3 mm long, 0.5 mm diam., acicular narrowing above, glabrous. Anthers five, before anthesis 2.3 mm long, 1.2 mm broad, orange tinged with red; apical gland 1.5 mm long, greenish and incurved at the glandular apex. Pollen about 69 µ long, 41 µ broad, oblong. Disc obvallate, a narrow rim level on top equalling the top of the stigma at first, green, exudes nectar. Stigma 0.8 mm diam., capitate, globose, dark green. Style becoming 1 mm long, persistent. Ovary 5-carpellate, 1 mm diam., apex pubescent. Fruit 5-carpellate, surrounded two-thirds of the way up by the persistent calyx lobes, 7.5 mm long, 4.7 mm diam., fringed with short spiky hairs on the margins and at the apex, gland-dotted; horns 1 mm long, erect, extremely-short, without any apical gland. Seed 5 mm long overall, 1.8 mm broad, black, shining; aril black on one side.