Sonneratia L.F.

Trees, evergreen, glabrous, columnar or spreading, not buttressed, surrounded by pencil-like pneumatophores arising from long, shallowly buried, horizontal roots. Leaves simple, opposite, borne in one plane, entire, leathery, apex often with a minute hydathode forming a thick mucro. Flowers 1-3 clustered at apex of ultimate, pendulous branchlets, actinomorphic, 4-8-merous, opening at night. Floral tube shallowly campanulate, at fruit maturity persistent, partly surrounding fruit or expanded and saucer-shaped with fruit fully exposed; sepals 4-8, adaxially green or red, thick, leathery. Petals red or white, lanceolate-linear, caducous, vestigial, or absent. Stamens numerous; filaments red or white; anthers reniform. Ovary superior to partly inferior, depressed, 10-20-carpellate. Fruit globose, berrylike, leathery, indehiscent, crowned by style base. Seeds numerous, embedded in foul-smelling pulp, irregularly angular or falcate; seed coat thickened, roughened, somewhat corky. 2n = 24.

Inhabitants of coral-terraces (either inundated by flood or not), shallow parts of calm seas, the mangrove and the banks of tidal rivers and creeks.The structure and functioning of the root-system of S. caseolaris has been studied by C. TROLL ( C. TROLL Ber. D.B.G. 48 1930 Gen.-Vers. Heft p. (81)-(99) Planta 13 1931 311-473 Trop. Natuur 22 1933 33-39 ). He has found that the so-called 'aerophores' are emitted by numerous long horizontal cable-roots and serve to produce fine nutrition roots penetrating horizontally in the uppermost layer of the steadily increasing (rejuvenated) silt. The aerophores themselves do not serve for respiration; this function belongs to the nutrition roots the production of which follows the deposition of silt layers. These observations are mutatis mutandis valid for all mangrove aerophores or pneumatophores (Fig. 1).It has appeared that S. caseolaris (L.) ENGL, can grow in fully fresh water without any connection with brackish water. It has been found along the shore of the Sentani Lake, at 75 m altitude, on sandy clay or peaty soil, and also along the Obehfareh R., near Hollandia, in the North of West New Guinea. Other plants occurring along the lake-shore are Crinum asiaticum L. and Pongamia pinnata (L.) MERR. which are otherwise largely confined to the sea-shore. This lake contains also several marine animals. It is accepted that it was, even in historical time, a lagoon in open connection with the sea which has become an inland lake by the rapid upheaval to which the northcoast of New Guinea is subjected. It is most curious that the species has been able to maintain itself. It produces the normal aerophores.Shortly afterwards we received material of the same species from East New Guinea, again from the northcoast, where Mr. J. S. WOMERSLEY collected it at 150 m altitude, in Morobe Distr., 10 miles from Lae, as a 9 m tall tree along the inner margin of a sago swamp, near Oomsis on Wau road (NGF15307), Aug. 15, 1962.Though it can be cultivated in fresh water, e.g. at Bogor Botanic Gardens, at 250 m alt., this is the first time it was found in fresh water under purely natural conditions. Obviously, if conditions are favourable and upheaval rapid, marine plants may maintain themselves for some time. The trees in question are not thick enough to have survived since the beginning of the upheaval which started some 4-5 centuries ago and must date from later generations. Also at Bogor regeneration takes place under freshwater conditions. Cf. STEEN. Nova Guinea, Bot. n. 12 1963 189 .A distribution map of the genus is published in Pac. Pl. Areas 2 1966 248-249 .

Uses. On the whole rather unimportant. The wood of S. alba is locally used for house-and boat-building, elsewhere only as (a rather inferior) fire-wood or not used at all. The young berries which have a sour taste are locally eaten; they are also used as a medicine. See for the extraction of pectin from the fruits under S. caseolaris (L.) ENGL.