Taxonomy of Alangium section Conostigma ( Alangiaceae )

Alangium Lam. sect. Conostigma Bloemb. is largely confined to the Malesian area and contains 19 species. By using the characters as found in the original species-descriptions, and with emphasizing the nature of the indument of the leaf bud, the confusingly variable Alangium javanicum s.l.-complex could be dismantled for a great part. Four new species: A. ledermannii, A. pallens, A. plumbeum, and A. subcordatum, and two new varieties: A. meyeri var. macilentum and A. ebenaceum var. insignis are recognised. Two taxa are raised to specific status: A. nobile subsp. denudatum to A. denudatum and A. javanicum var. minahassicum to A. minahassicum. A key to the species is presented, and the concerned taxa are enumerated, referenced, described and some are figured.

Habitat & Ecology -Lowland mixed dipterocarp forest, flatland or undulating country, along rivers and hillside, also in swampy forest; basalt, sandy clay, podsoil, and (yellow) sandy soil; from sea level to 600 m altitude; flowering and fruiting all year round.
Field-notes -Stilt-roots and buttresses recorded; bark smooth; fruits edible, green ripening pinkish or red.
Note -Alangium borneense resembles A. mezianum; the latter is generally stouter in all parts (but not the fruit), its tomentum of twig apex and leaf bud is shorter (hairs 0.2-0.3mm only), its leaf bud is (almost) straight, and its filaments are hairy at apex.In A. borneense the leaf bud is characteristically strongly in-curved and densely woolly hairy, not allowing to see the juvenile lateral veins, and its filaments are glabrous.
Fruit not known.Distribution -Borneo (Sarawak), only known from the type.
Habitat & Ecology -Disturbed primary heath forest; white podsolised soil; flowering in October.Proposed IUCN (2012) conservation assessment -Critically Endangered (CR), since the type locality no longer exists and the species is only known from the type collection.
Notes -1.We checked the hairiness of the locule inside as mentioned by Stone & Kochummen (1975); with a magnification of ×60 we could detect some minute hairs.
2. The Sarawak botanist Julia Sang informed us that Bukit Siol (now within Kuching town) is converted into human settlement and that in 1964 when A. circulare was collected the forest type was heath forest on podsolised white soil.
Habitat & Ecology -Marsh forest (mixed peat swamp forest), at sea level; flowering in January and July; fruiting in April and July.
Habitat & Ecology -Mixed dipterocarp forest, thick (old) secondary forest on steep slope of river-valley, on fertile loamy ground; 50-160 m altitude; fruiting in February, August, and September.
Note -Because of the apparent absence of a duplicate of the destroyed holotype a neotype is herewith designated.
Habitat & Ecology -Dry land lowland forest on low hills; sandy loam soil with lime; to 250 m altitude; flowering in July and August; fruiting from July to February.
Field-note -Ripe fruit red.
Notes -1.Alangium javanicum is variable, possibly also in the hairiness of the leaf buds; see also the notes under A. oblongum and A. meyeri.
2. The distribution area of A. javanicum is determined as restricted to W Java and E Kalimantan (1 collection, Kostermans 4365, Sungei Riko, Balikpapan).
It should be noted that according to Bloembergen (1939: 222) the type of the synonym Marlea costata originates from Lampong, S Sumatra, cultivated in the Bogor Botanical Garden (from Teijsmann 6717); however, the annotation 'Teijsmann 6717' on the holotype of M. costata (L L0009823) is lacking and its provenance cannot be proven.
In addition there are in L three collections from outside Java which cannot go with other species, but which also do not fully match our present conception of A. javanica.They are: Neth.Ind. For.Service bb 22406, N Sumatra, Aceh, G. Agusan, ± 1800 m alt., fr.; Neth.Ind. For.Service bb 26597, SE Kalimantan, upper Mahakam River, low alt., fr.(fruit different from bb 22406); Leighton 106, E Kalimantan, Kutei, low alt., fr.).More, similar material from these areas is needed in order to place these collections.Note -The flowers of A. kayuniga are herewith described for the first time (Yii & Asah S 64913; Hou 403).The species is close to A. meyeri var.macilentum, which differs mainly in the presence of a minute but distinct indument.In the cited collections the red-brown calyx limb contrasts with the yellowish ovary and corolla in bud.Etymology.The specific epithet refers to the Swiss botanist Carl Ludwig Ledermann, who in 1912/13 joined an expedition along the Empress Augusta River (Sepik River).
Habitat & Ecology -Dense, moist primary rain forest with ferns and mosses; 200-400 m altitude; flowering in November.
Proposed IUCN (2012) conservation assessment -Data Deficient (DD), although there is concern as the species has been collected only twice.
Habitat & Ecology -Primary forest, in flat terrain and sloping hill side; loamy soil with stones, sandy clay soil, rocky soil; from sea level to 100 m altitude; flowering in November (one collection); fruiting in May, July and October, but most collections sterile.
Etymology.The name macilentum (Latin = meager) refers to the delicate stature of the twigs with smaller leaves, flowers, and fruit.
Tree 10-25 m tall.Twigs 1.5-2(-2.5)mm diam, minutely hairy (hairs 0.1 mm long or less).Note -Alangium meyeri var.macilentum denotes specimens of A. meyeri which differ from the type variety in their diminutive habit; it approaches A. kayuniga, which differs chiefly in almost lacking any indument.Alangium meyeri var.macilentum also links up with meager specimens provisionally reckoned as belonging to A. javanicum from SE Kalimantan, the latter distinct in a much more conspicuous indument of hairs c. 0.5 mm long on twig apex and leaf bud.With magnification one can see that var.macilentum has a dense covering of minute hairs less than 0.1 mm long.
Field-notes -Mature fruits dull reddish or dull purple; buttresses and small or large stilt roots recorded.
Notes -1.Alangium mezianum is close to A. borneense, the latter generally with smaller dimensions in most parts, and differing especially in a more conspicuous indument of the curved leaf bud.
Habitat & Ecology -Primary forest, on hillside, steep terrain, near river bank; loamy soil with little humus, sandy soil, clayey soil with stones, black volcanic soil, on shale quartzite bedrock, also on limestone; from sea level to 700 m altitude; flowering and fruiting predominantly from October to December and March.
Field-notes -Often recorded as a solitary tall tree with a straight bole; bark smooth; prop roots, buttresses, and small stilt roots exist; flowers very fragrant.The ripening colour of the fruit is not recorded.
Habitat & Ecology -In lowland dry forest, mixed dipterocarp forest, ridge bamboo forest, hill slope in kerangas forest, and along river banks; on sandstone, yellow clay, clayey soil, yellow sandy soil; from sea level to 700 m altitude; flowering and fruiting all year round.
Field-notes -A very handsome large tree; plank buttresses 2 m high extending to 2 m over the ground, narrow; bole fluted to 5 m; bark smooth, thin; fruit reddish.
Uses -Wood for constructions and canoes.Field-notes -Van Balgooy et al. 5357: "fruit purple, 1 seed covered by a white sweet sour juicy carcotesta, edible, favourite food of pigs and primates, very common" and Argent 9615 et al. "tree with bright red edible fruit, brought into camp to be eaten".Bark whitish or whitish brown; stilt roots and buttresses recorded.
2. It could be imagined that three here accepted species, viz. A. oblongum, A. meyeri, and A. ridleyi are exponents of one single species, only differing in sizes and in facies, as there seem to be sufficient intermediates to connect them.However, we do not believe this, as it readily appears incredible to unite e.g.'typical' A. ridleyi from Singapore, a plant with robust twigs, with A. meyeri, a plant of much more delicate stature, from Luzon.On the other hand, also A. javanicum (a species with obvious hairy leaf bud, and small fruits, 15 -20 mm long), seems to intergrade with A. meyeri, typically with an indument of minute scale-like hairs.In this way, the 'javanicum complex' problem, as alluded to in the introduction, is replaced by a smaller 'oblongum complex' problem which again needs further study; probably some more not yet defined taxa are involved.
Habitat & Ecology -Primary and secondary forest, on river banks, sand stone rocks; brownish sandy soil, sandstone, and limestone; from sea level to 700 m altitude; flowering in March, May, June, October; fruiting in March, May, July, August, December.
Field-notes -Strongly fluted trunk and buttresses recorded; fruit ripening pink-red or wine-red.
Etymology.The specific epithet plumbeum (Latin = leaden grey) refers to the drying colour of the leaves.
Habitat & Ecology -Primary & secondary forest, also swamp forest; on sandstone; at low altitudes; flowering April to July; fruiting in November, January and May.
Note -Material from Borneo, at present treated under Alangium ridleyi, could be erroneously regarded as belonging to A. oblongum.As noted under A. oblongum, the distinction between the two species is not easy and sometimes not clear.In A. ridleyi, however, the filaments are broader, and hairy at the apex, in A. oblongum the filaments are comparatively narrower, and hairy almost all over.
Etymology.The specific epithet refers to the leaf base.
Habitat & Ecology -Primary rain forest, on slope and flat ground; 100-150 m altitude; flowering in January and March; fruiting in March and September.
Field-notes -Strongly buttressed; bark grey brown or light grey, smooth, exfoliating in rounded flakes leaving a sculptured surface; fruit laterally compressed.
Proposed IUCN (2012) conservation assessment -Data Deficient (DD), although there is concern as the species has been collected only thrice in a restricted area in lowland rain forest.
We have not found the Jaheri collection and we do not know whether Bloembergen when describing the variety had a leafy twig at hand or only fruit, but we assume that the described fruit belongs to the section Conostigma.The variety may belong to A. minahassicum (fruit smooth) or to A. hollrungii (fruit presumably smooth).When the described ribs are not an artefact, it may represent a distinct taxon.
Acknowledgements This article is for a large part based on the overall revision of the genus Alangium by Bloembergen (1939).We thank the curators of BK, BKF, BO, K, L, QBG, and SING for allowing us to study their collections.Especially the authors are grateful for the one month grant from SING, in 2015, in order to study the Singapore collection and by which they could also see material from living trees.In continuation to their stay in Singapore the authors examined the Alangium specimens at BO for two weeks.As usual, the artist Jan van Os (L) prepared the illustrations.
In the Leiden herbarium helpful analytical drawings of flowers and (parts) of inflorescences were found with the sheets, representing most taxa.Although almost anonymous, it appeared that they were made in 1972 by Mrs E.L. Fluyt, a student of the late Marius Jacobs, studying Alangium intended for Flora Malesiana.