270 MR. H. N. RIDLEY ON THE FLORA OF THE 
of the rainfall. During а tropical shower it is easy to see how well the commonest 
form of jungle-leaf (a lanceolate acuminate or caudate one) is adapted for throwing off 
the heavy rainfall rapidly. But the form of the narrow leaf among the plants mentioned 
above seemed to me to be the result of adaptation to avoid another danger. 
АП these plants grow on rocks close to the water's edge, and as the river is subject to 
very rapid rises from sudden falls in the mountain districts, these plants are liable to 
submersion in a violent rush of water. Broad foliage would be torn off or mutilated, 
but narrower leaves, offering a less resistance to the water, would receive no injury. 
One may compare with this the narrow floating leaves of the aquatic Ranunculi and 
Potamogetons which inhabit the rapid streams in Europe. 
The islands of the Tahan River formed of boulders produced several interesting plants, 
including Homonoia, not hitherto recorded south of Siam, a curious new and shrubby 
Phylianthus, and abundance of the beautiful orchid Arwndina speciosa, Blume. 
Many smaller streams run down from the sides of the hills to join the main river, and 
in their ravines were Begonias, Aroids, Didymocarpi of all colours, and the curious Gom- 
phostemmas, resembling the European Lamium and Galeobdolon, and many Scitamineze. 
The soil of these woods is very sandy in many parts and it is probable that to this 
cause the paucity of Termites is due. They were certainly much less abundant than they 
are in the woods in the island of Singapore and the southern part of the Peninsula 
generally. Owing to this the leaves and sticks on the ground decayed slowly and formed 
aricher soil, while in the woods on clayey soil, where white ants are abundant, the 
vegetable fragments are rapidly eaten by them as they fall and are rendered useless for 
soil-fertilization. The Termites are unable to live in sandy soil, because they cannot 
make their subterranean nests in sand, which would fall in, whereas in the stiffer clay 
they can easily make the dome-shaped chambers and passages. 
The upper woods of the Tahan River were very wet, rain falling heavily every night. 
The ground was permanently sodden, and at night glowed brilliantly with the luminosity 
—probably Bacterial—of the decaying leaves. At the furthest point to which the 
expedition attained, a fair-sized stream entered on the right bank of the main river, and 
here the trees were covered thickly with wet moss, in which grew many orchids, including 
a new species of Phalenopsis allied to Р. sumatrana, a beautiful orange-flowered Den- 
drobiwm, Calogynes, and Erias. In the muddier spots were many fine Scitaminex; 
Phryniums of two species, Globba, Curcuma, Amomums, and Zingibers were obtained. 
In the drier upper part of the hills grew the beautiful palm called by the natives “ Daun 
Payoh ” (umbrella-leaf), the Zeysmannia altifrons, Miq. 
Jungle-products. 
The dense jungles of the Tahan River produce a good quantity of Rattans of many 
species, but in the more accessible country along the banks of the Tembeling and Pahang 
Rivers, the better class of Rattans have been almost exterminated and little is left but 
the inferior ones, especially Calamus crinitus, Blume. dS 
Of Dammar-trees the * Minyak Krueng ” (Dipterocarpus pterygocalyz, Miq.) and a few 
other species are abundant. Gaharu-wood (Aquilaria malaccensis, Hook. f.) is collected 
