Confined to the southwest quarter of Sri Lanka, these multi-storied forests are some of the richest in the World with a density of species approaching the highest of all the World’s natural jungles. Above the canopy, is usually an emergent layer of very tall trees, up to 38 m high, such as Dipterocarpus zeylanicus, Doona congestifolia, Pygeum zeylanicum, Xylopia parvifolia, together with endemics like Cryptocaraya membranaceae (Lauraceae), Canarium zeylanicum (Burseraceae), Diptercarpus hispidus, Hopea discolor, Shorea lissophylla (Dipterocarpaceae), Mangifera zeylanicum (Anacardiaceae) and Palaquium grande (Sapotaceae). The canopy and sub canopy layers typically comprise Adenanthera pavonina, Chaetocarpus castanocarpus, Cullenia excelsa, Cyathocalyx zeylanicus, Ficus callosa, Harpullia arborea, Horsfieldia iriya, Iilex zeylanica, Isonandra lanceolata, Kokoona zeylanicus, Kurrima zeylanica, Lasianthera apicalis, Litsea glutinosa, Mesua ferrea, Mimusops elengi, Pometia exima, Pygeum zeylanicum, Scutinanthe brunnea, Strombosia zeylanica, Trichadenia zeylinica, Urandra apicaulis, and endemics such as Anisophyllea cinnamomoides (Anisophylleaceae), Artocarpus nobilis (Moraceae), Camnosperma zeylanica, Semecarpus gardneri (Anacardiaceae), Carallia calycina (Rhizophoraceae), Chaetocarpus coriaceus (Euphorbiaceae), Diospyros quaesita (Ebenaceae), Horsfieldia iriyaghedhi, Myristica dactyloides (Myristicaceae), Hydnocarpus octandra, Trichadenia zeylanica (Flacourtiaceae), Mastixia tetrandra (Cornaceae), Pseudocarapa championii (Meliaceae), Shorea stipularis (Dipterocarpaceae), Syzygium makul (Myrtaceae) and Terminalia parviflora (Combretaceae).

Below the canopy is lower story of medium sized trees principally comprised of Adenanthera aglaeosperma, Aporosa latifolia, Axinandra lanceolata, Calophyllum pulcherrimum, Chrysophyllum roxburghic, Cinnamomum zeylanicum, Cleidion javanicum, Dillenia retusa, Eleocarpus serratus, Garcinia cambogia, Gironniera cuspidata, Hollarhena mitis, Julostylis angustifolia, Lannea grandis, Litsea cauliflora, Macaranga digyna, Machilus macrantha, Mallotus alba, Ochna wightiana, Pterygota thwaitesii, Rejoua dichotoma, Symplocos cuneata, Syzygium aquem, Trema orientalis, Turpinia malabarica and Wormia triquetra. The endemic trees of this layer include Bridelia moonii (Euphorbiaceae), Brysophyllum ellipticum, Timonius jambosella (Rubiaceae), Goniothalamus hookerii (Annonaceae), Litsea longifolia (Lauraceae), Semicarpus moonii (Anacardiaceae), Syzygium firmum, S. neesianum (Myrtaceae) and Stemonopurus cordifolium (Dipterocarpaceae).

The shrub layer includes various small trees and shrubs such as Agristitachys longifolia, Aporosa lindleyana, Desmos elegans, Diospyros insignia, Gaetnera vaginans, Gyrinops walla, Humboldtii laurifolia, Ixora coccinea, Lasianthus strigosus, Leea sambucina, Schumacheria castaneaefolia, and Symplocos coronata together with endemics such as Semecarpus pubescens (Anacardiaceae) and Sysygium spissum (Myrtaceae). The field layer is usually rich in ferns and aroids, while other common plants include Apama siliquosa, Calamus zeylanicus, Ellettaria cardmomum, Ochlandra stridula, Polyalthia acuminata, Psychotria nigra, Schizostigma hursuta, Symplocos minor, Todalia aculeata and the endemic Memycylon arnottianum (Melastomataceae).  Lianas, climbers and epiphytes are well represented. Typical climbers and lianas found on some of the larger trees include Acacia concinna, Angistrocladus vahlie, Connarus monocarpus, Coscinium fenestratum, Dalbergia championi, Derris scandens, Entada scandens and Tetracera scandens. Ferns, lichens and orchids dominate the epiphyte flora with common epiphytic orchids including Liparis longipes, Pholidota imbricata and Sarchohilus pulchellus.

References

Campbell, D. G. & Hammond, H. D. 1989. Floristic Inventory of Tropical Countries. The New York Botanical Garden.

De Vlas, J. & de Vlas-de Jong, J. 2008. Illustrated field guide to the flowers of Sri Lanka. Mark Booksellers and Distributors (Pvt) Ltd.

Fernando, D. 1954. Wild Flowers of Ceylon. West Brothers, Mitcham.

Fernando, S. N. U. 1968. The Natural Vegetation of Ceylon. Colombo: Swabasha.

Gunatilleke, I. A. U. N. & Gunatilleke C. V. S. 1991. Woody endemics of the wet lowlands of Sri Lanka and their conservation. Biological Conservation, 55: 17-36.

Gunawardenia, D. C. 1968. The Flowering Plants of Ceylon. Lake House Investments Ltd.

Puri, G. S., Gupta, R. K., Meher-Homji, V. M. & Puri, S. 1989. Forest Ecology. Plant form, diversity, communities and succession. 2nd Edition. Volume 2. Oxford & IBH Publishing Co. PVT. Ltd.

Sumithraarachchi, D. B. 1989. Sri Lankan forests: diversity and genetic resources. In: Tropical Forests - Botanical Dynamics, Speciation and Diversity. Eds. L. B. Holm-Nielsen, I. C. Nielsen and H. Balslev. Academic Press.

Thwaites, G. H. K. 1864. Ceylon Plants. Dulau & Co.