KUNGL. SV. VET. AKADEMIENS HANDUNGAR. BAND 50. N:0 8. 5 



The LiUoral forests only occupy a small area and are to be found chiefly on 

 or near the sea-shore, where the land is low-lying and chiefly mud. The largest 

 are then round the mouth of the Menam Chao Phaya river and along the northern 

 shore of the Giilf of Siarn. In general they are composed of species of the order 

 Rhizophoracece called Mangrove. Some of the most impenetrable jimgles are to be 

 found in the Littoral forests. The Mangrove is always replaced by Casuarina trees 

 where the mud gives place to sand. I only passed these forests, without trying to 

 explore them, so I cannot give information about their bird-life. 



The Tropical Evergreen for ests are confined to two broad belts, the one passing 

 from Chantaburi along the eastern frontier districts, and the other from the southern- 

 most parts of Siam up to the districts in the west towards Tenasserim and Burma. 

 The first-mentioned belt reaches the coast in the south and then foUows the moun- 

 tains to the Mekong river. The second belt clothes the mountains and valleys of 

 southern Siam and is conterminous with the forests in Tenasserim and Burma and 

 finally merges into the Semi-tropical forests in Northern Siam. 



In the eastern evergreen belt the most common trees are the gigantic Diptero- 

 carpus turbinatus and Hopea odorata; in the western forests of Central Siam on the 

 contrary the most abundant tree is Xylia xylocarpa mixed with species of Buxus 

 and CoRsalpinia. 



The Tropical Evergreen forests pass över in Northern Siam at high elevations 

 on the mountains to the Semi-temperate evergreen j orests and these are distinguished 

 by a mingling of trees from the temperate zone with tliose from the Tropics. Several 

 species of bamboos and palms are here interspersed among pines and oaks all ever- 

 green. In no Semi-temperate evergreen forests is there much undergrowth and as a 

 rule the trees are not so high as in the Tropical evergreen forests. 



In the Laierite forests there are only trees to be found which are peculiar to 

 a laterite soil. The most abundant trees are Pentacme siamensis, Shorea obtusa and 

 Dipterocarpus tuberculatus. The undergrowth chiefly consists of very high grass which 

 becomes completely dry during the hot season. The Laterite forests cover the grea- 

 test parts of Eastern Siam and they are always thin with open places here and there. 



The Dry mixed forests are closely related to the Laterite forests, but they only 

 occur in places where the soil is not lateritic, but where other conditions are the 

 same as in the latter. The Dry mixed forests are chiefly composed of bamboos 

 and they always present a thin appearance. One of the most valuable trees to be 

 found here is the Lagerstroemia flos regina. 



The Dry mixed forests pass över into the great Deciduous forests of Northern 

 Siam where the teak tree {Tectona grandis) is the most abundant and also the most 

 valuable. The teak forests are situated in the dry regions of the Monthon Payap 

 and part of some other Monthons (= provinces) which lie north of Lat. 17°. All these 

 regions are hilly throughout and are drained by the Salween, the Mekong and the 

 feeders of the Menam Chao Phaya river. 



