ENG-1974 — Page 280

NATURAL HISTORY

Flora

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Hong Kong possesses a large and diverse flora of vascular plants-estimated at about 2,400 species, native and introduced-for so small an area. Generally Hong Kong offers the northern limit of tropical Asian flora.

Few tall trees are to be found except in the fine fung shui groves around many villages in the New Territories. After centuries of cutting, burning and exposure, the barren hillsides present a dry and arid impression. The ravines, saved from man and fire by their rugged character and more moist winters, contain a dense vegetation particularly rich in low trees, flowering shrubs and ferns. However, many hill slopes, particularly those in the water catchment areas, have been replanted by sowing tree- seeds or planting tree-seedlings raised in nurseries.

It is to conservation of wooded areas by the Agriculture and Fisheries Depart- ment that Hong Kong owes much of its mixed woodland. In a few large ravines, particularly Tai Po Kau and Pok Fu Lam Valley, autumn and spring colours are particularly noticeable. There are several trees, shrubs and climbers whose leaves change to brilliant colours in autumn. Plants which show richest autumn colours con- tinue their display into February, before the start of spring. Many trees, shrubs and vines help to produce this effect-Liquidambar formosana, Rhus spp, Sapium spp, Mi- chilus thunbergii, Raphiolepis indica, Rourea microphylla, and Vitis cantoniensis.

Many plants in Hong Kong are exceptional for the beauty or fragrance of their blossoms. The Bauhinia blakeana (Hong Kong Orchid Tree) was discovered in 1908 at Pok Fu Lam and was named after former Governor, Sir Henry Blake. It is among the finest of the Bauhinia genus anywhere in the world and has been adopted as Hong Kong's floral emblem. It is now quite widely planted.

Other plants produce fruits that are pecked at and eaten by birds. A common tree, the Sterculia is an example. The remarkable starlike fruit turns crimson in late summer and splits open to disclose the jet black seeds. The seeds are eaten by a number of birds including the Chinese Blue Magpie.

A great variety of wild plants have medicinal and economic values. Parts of a common tree, Schefflera octophylla, are used in herbal medicines for the preparation of 'leung cha', a drink used chiefly for relieving indigestion. Shrubs like Psychotria rubra, Ardisia crispa and Strophanthus divaricatus are thought useful for bruises and certain injuries.

Botanical explorations carried out by staff of the Hong Kong Herbarium, staff of the two universities and amateur botanists, have been fruitful. Since the publication of the Checklist of Hong Kong Plants (1966) there have been 43 new additions to the Hong Kong flora.

More than 90 species of nature orchids are recorded. Some ground orchids are beautiful and have long been cultivated in other countries. Probably the best known of the local species is the Nun Orchid, bearing flowers four inches across with white petals and a purple lip. A new species with greenish cream-white flowers was dis- covered in 1969 by Dr S. Y. Hu and was named Cymbidium maclehoseae in honour