Gymnostoma sumatranum
| Gymnostoma sumatranum | |
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| Common Ironwood (Casuarina equisetifolia) | |
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| Family: | Casuarinaceae |
| Genus: | Gymnostoma
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| Species: | Gymnostoma sumatranum
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Gymnostoma sumatranum is of the [Casuarinaceae] family of dicotyledonous flowering plantswhich are in the order Fagales. The family consists of 4 genera and approximately 70 species of trees and shrubs native to the Old World tropics (Indo-Malaysia), Australia, and the Pacific islands. At one time, all of the species were placed in the genus Casuarina, but these are now split among Allocasuarina, Casuarina, Ceuthostoma, and Gymnostoma. (1,2,3,4)
Morphology: Gymnostoma sumatranum and the other members of this family are characterized by drooping equisetoid (meaning "to look like Equisetum") twigs, are evergreen, and monoecious or dioecious. The roots have nitrogen-fixing nodules that contain the soil actinomycete Frankia. This foliage of this tropical tree looks like that of the Pine trees which grows in temperate climates. Casuarina equisetifolia is typified by its rough straggling appearence, whilst Gymnostoma sumatranum is characterised by its multiple rounded umbrella shaped crowns. The stems are angular or tetrahedal in cross section (2). The Stomata are not restricted to sunken grooves, (2). The female inflorescences are borne terminally (2).
Habitat:
In Malaysia, Gymnostoma sumatranum is known as Rhu Bukit - bukit in Malaysian means hill. The other common species in Malaysia is Casuarina equistetifolia known as Rhu laut - laut in Malaysian means sea and typically it grows along the sea shore in sandy substrates. In Sarawak it is a protected species (5). Gymnostoma sumatranum grows further inland and in coastal regions it is a good indicator that the soil is dry and out of the littoral and inundation zone since it will not normally tolerate sandy or boggy soil.
References
(1) Dilcher, D. L. et al. (1990) Evolution of the CASUARINACEAE: morphological comparisons of some extant species. American journal of Botany. 77(3): 338-355. 1990.
(2) P. S. Green, Klaus Kubitzki, E. Götz, K. U. Kramer. (1990) The Families and Genera of Vascular Plants. Published by springer. 404 pages
(3) Jane N. Prider and David C. Christophel Distributional ecology of Gymnostoma australianum (Casuarinaceae), a putative palaeoendemic of Australian wet tropic forests. Australian Journal of Botany 48(4) 427 - 434
(4) Barlow, B.A., (1983). Casuarina Ecology,. Management and Utilization. edited by S.J.Midgely. pp. 10–18
(5) http://www.sarawakforestry.com/htm/snp-bc-pp.asp Sarawak Forestry ordinance 1998.