Botanical Survey of India | Flora of India

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Dipterocarpus retusus Blume, Catalogus 77. 1823. D.macrocarpus Vesque in Compt.- Rent. 78: 627.1870.

Asm.: Hollong, Holong, Dhuliya gurjan, Dholi gurjan,· Eng.: Hollong.

Trees, ca 50 m tall; bole cylindrical, ca 5.5 m in girth; bark pale bluish-grey outside, smooth with large, raised tubercles at the base of stem, reddish-brown inside, 1.7 - 2.2 cm thick; branchlets, panicles, calyx and corolla outside densely buff puberulent or glabrous; petiole, vegetative bud and ovary rufous silky tomentose or glabrous. Leaves 15 - 25 x 10 - 15 cm, elliptic to elliptic-obovate, rounded at base, abruptly acuminate or cuspidate at apex, repand or corrugate, membranous, densely brown ciliate with fas-cicled hairs; lateral nerves 18 - 25 pairs, tertiary nerves transverse, subparallel with reticulations in between; petioles ca 5 cm long, sparsely pilose; stipules 7.5 - 12.5 cm long, membranous, densely pilose outside with long fascicled hairs, glabrous and punc-tuate inside with the bases of the outside hairs. Flowers 3 - 6 in ca 7.5 cm long, axillary spikes. Calyx tube ca 1.5 x 1.3 cm at the mouth, turbinate, velvety puberulous outside, silky pubescent inside, three shorter lobes ca 2 mm long, deltoid-triangular, erect, two enlarged lobes 20 - 25 x 3 - 5 mm, strap-shaped, coriaceous, velvety. Corolla lobes falcate, oblanceolate, membranous, especially towards tip and margins, faintly longitudi-nally nerved, g1abrate inside, stellate-puberulous in close, horizontal bands outside except on overlapped parts. Stamens 30, longer than style at anthesis; filaments filiform, dilated at base; anthers 5 - 8 mm long, linear-oblong, tapering, connective appendage ca 4 mm long, subulate. Ovary 6 x 4 mm, ovoid, silky pubescent, obscurely longitudinally ribbed; styles ca 1.5 cm long, longitudinally ribbed, silky hairy in the basal two-thirds portion. Fruit ca 5 x 4.2 cm, calyx tube glabrate and minutely punctate with stellate bases of fallen hairs; 3 smaller lobes of fruiting calyx ca 2 x 1.5 cm, orbicular ovate or ovate-elliptic, obtuse, subrevolute, 2 enlarged lobes 15 - 27 x 3.7 - 5 cm, tapering abruptly, ca 1.3 cm wide at base, leathery, puberulous, reticulately veined with 3 strong main nerves.

Fl. June - Nov.; Fr. Aug. - March.

Distrib. India: In tropical wet evergreen forests up to 1000 m. West Bengal (North-ern parts) Assam, Arunachal Pradesh and Nagaland.

Thailand, Indo-China and Malesia (Java and Malay Islands)

Notes. It grows gregariously in the forests of Sibsagar and Lakhimpur in Assam. The distribution, density and persistence of the tomentum is very variable even within a single population.

This species is reported to be closely allied to D.baudii Korthals (in habiting the lowland Dipterocarp forests in Burma, Thailand, Cambodia and S.Vietnam), but can be easily distinguished from the latter by its glabrous mature leaves and with marked ridges between the lateral nerves.

A well-known plywood species of Eastern India. Wood used for making tea chests, packing cases and for making railway sleepers after treatment.

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