Ristantia pachysperma (F.M.Bailey) Peter G.Wilson & J.T.Waterh.

Myrtaceae

Wilson, Peter G. & Waterhouse, J.T. (1982) Australian Journal of Botany 30: 443.

Penda, Yellow; Sour Hardwood; Yellow Penda; Johnstone River Yellowwood

The bark of the larger trees marked by long fissures. Blaze fibres interlocked, i.e. the fibres in different blaze layers are aligned in different directions. Blaze darkens on exposure.

Pale brown oil dots visible with a lens. Leaf blades about 8-21 x 4-10.5 cm. Lateral veins curving inside the margin but not forming definite loops.

Inflorescence up to 10 cm long. Sepals broadly triangular, about 1 mm long. Petals +/- orbicular, about 2-3 mm long. Stamens about 100, filaments up to 2 mm long. Style about 0.2-0.3 mm long.

Fruit dehiscence limited by the thickened fruiting hypanthium which is well developed beneath the capsule. Fruiting hypanthium flat to very broadly obconical, rim not reflexed. Fruits about 15-20 mm diam. Seeds somewhat flattened +/- ovate, about 7-8 x 6-7 mm, testa +/- smooth. Cotyledons contorted and folded.

Cotyledons bilobed, +/- butterfly-shaped, apex broadly emarginate, base truncate to cordate. Oil dots numerous, reddish. At the tenth leaf stage: leaf blade obovate, apex obtuse, base attenuate but abruptly narrowed into the petiole, upper surface very finely hairy; oil dots numerous, visible with a lens; petiole clothed in short, prostrate, pale brown hairs.

Endemic to NEQ, restricted to the area between Cape Tribulation and Mourilyan. Altitudinal range from sea level to 100 m. Grows in well developed lowland rain forest often on the margins of freshwater swamps.

Produces a general purpose structural timber.

Wood specific gravity 0.81. Cause et al. (1989).

Metrosideros pachysperma (Bailey) F.Muell., Second Systematic Census of Australian Plants : 100(1889). Tristania pachysperma (Bailey) W.D.Francis, The Queensland Naturalist 14: 56(1951). Xanthostemon pachyspermus F.Muell & F.M.Bailey, Occas. Pap. Queensland Flora 1: 4(1886), Type: Lecto: Johnstone River, T. L. Bancroft; holo: Bri 13083; syn: MEL, NSW. [Fide Wilson & Waterhouse (1982).].