517 
supply of oxygen is very small but they are often very conspicuous 
and striking in the wet swamp woods of the interior. Their 
presence shows conclusively that there is not sufficient oxygen in the 
soil for the plants growing there. Again “ Livingstone arrives at 
the conclusion that at least in some bogwater there occur chemical 
substances which are not in direct relation to the acidity of the 
water but which act on the vegetation, and it is suggested that these 
substances may play an important role in the inhibition from bogs 
of plants other than those exhibiting xerophytic adaptations ” 
(Warming). 
The most important factor, or as Warming expresses it “ the 
weightiest cause of the physiological dryness of the soil lies in the 
humic acid and other dissolved substances which chemically affect 
the roots. Humous acids depress the roots activity, and render it 
more difficult for the plant to replace the water lost by 
transpiration. ” 
It may be pointed out, too, that these lands where this soil 
formation occurs are quite flat and consequently fully exposed to 
winds when cleared of forest for planting. In fact one feels the 
wind sweeping through the cleared ground and sees the seedling 
rubber plants bending and quivering before it. Now wind has more 
than one injurious effect on young plants exposed to it.' Constantly 
moving the stem of a young plant, it keeps it loose in the soil and 
breaks the rootlets and root hairs as they grow, so checking the 
growth of the plant. But wind also does more. It increases the 
loss of water by transpiration. The loss of water would be 
sufficiently bad if the plants were protected from wind, but when by 
clearing the forest the loss is increased by the exposure to the action 
of the wind what chance has a hygrophytic plant like Para-rubber of 
existing? The injurious action of wind in increasing the loss of water 
has been overlooked or. not realised by planters who bare every hill 
top overlooking the estate to plant more rubber on it instead of 
leaving windbelts to check this loss of water in the young plants. 
It is probable that this loss of water by transpiration is the cause of 
that peculiar wrinkled appearance of rubber leaves that one so 
constantly sees in wind-swept young plants, but this requires 
further investigation. Hevea braziliensis possesses none of the 
adaptation for living in a dry or zerophytic region. Plants adapted 
for such a region are often protected from excessive loss of water by 
having the lower leaf surface covered with wax or hairs, by having 
a thick cuticle to the leaves, by having narrow leaves or leaves so 
arranged as to present the narrowest surface to the air and in various 
other ways. The leaves of Para-rubber are thin, neither protected 
by hair or wax ; they are broad and flat, so as to get the freest 
transpiration in their normal habitat, dense damp shady forests. 
By planting them on ground where the transpiration or loss of 
water is excessive, as in these peat lands, we submit them to the 
same state of affairs as if we planted them in the desert. When we 
