Dipterocarpus macrocarpus Vesque

Local name: হলং (Hollong)
Scientific Name: Dipterocarpus macrocarpus Vesque
Family: Dipterocarpaceae
Recognition: State tree of Assam
Conservation status: Critically Endangered

General characteristics: Hollong is a large tree and plant height reach upto 45 meter. Tree trunk may be upto 6 meter in diameter. Young shoots and petioles are covered with reddish-brown hairs. Leaves are elliptic-oblong, shortly acuminate at apex with a size of  25 – 45 × 14 – 25 cm, membranous, glabrous when mature. Flowers usually solitary, 5.8 – 7.5 cm long. Calyx-tube turbinate, silky-pubescent inside, velvety-puberulous outside. Petals 5, subfalcately oblanceolate, ca 6.5 × 1.5 – 2 cm, membranous, imbricate pinkish. Stamens ca 30; filaments dilated at base; anthers oblong with a pair of tubercles at base. Ovary ovoid, 5 – 6 × 3 – 4 mm, silky-pubescent; style ca 1.5 cm long, tapering from the top of the ovary. Fruits ovoid, ca 5 × 3.5 cm with enlarged wing-like calyx lobes (Pagag & Singh).

Flowering & Fruiting: June – July and January – March

Range of Distribution: India, Myanmar, Indonesia, Malaysia, Thailand, Laos and Vietnam

Local distribution: This plant is widely distributed in Dihing patkai national Park, Dibrugarh district.

Economic Importance: The timber is used in construction of house, especially for planking. Wood used for plywood, internal construction work and also used as railway sleepers. Oleoresin from the tree used as lubricant and in soap works (Pagag & Singh).

Global conservation status: Plant is in IUCN Red Listed category and it is critically endangered.

Regional threat: Due to high demand of its timber and superior wood quality plant is under severe threat from local people. Illegal and over exploitation creates a substantial threat on the plant.  

References:

K. Pagag & S.K. Singh. Botanical Survey of India, Eastern Regional Centre, Shillong.