403 
there is now scarcely any rubber in the Colony and most of thas 
which passes through the Gambia comes from French territory 
The returns of the export of rubber from this region are given at 
1904 — 30,934 lbs. value £2,446 
1905“ 9,071 lbs „ £ 9 ' 5 ‘ 
In Indo-China. 
“ Indo-China produced for export 3672 tons of rubber valued at 
£97,150; £1,245 worth was also bought in from neighbouring 
countries and re-exported. ” Most of this rubber is the product of 
a wild creeping plant and is collected in the forests of Tonkin and 
Laos by Natives. The supply of it has suffered from the reckless 
and wasteful manner in which the harvest was made when the in- 
habitants first found that they were able to get a good price for it. 
Steps are now being taken to prevent this waste and to instruct the 
Natives in the proper method of collecting the rubber. 
H. N. R. 
NOTES ON THE ACTION OF 
COPPER SULPHATE ON AQUATIC .PLANTS. 
The following notes on the submerged plants of our ponds and 
ditches are though incomplete perhaps worthy of record. The ex- 
periments on the action of sulphate of copper on these plants would 
have been continued but for lack of time to do so. 
What may be termed natural ponds or lakes, such as one finds 
in most parts of the world, are very uncommon in the Malay Penin- 
sula, and artificial ponds usually unless very deep become silted up 
very soon owing to the great denudation of the surrounding soil. 
Consequently the number of indigenous aquatic flowering plants 
in the Peninsula is not large. The chief bearing of importance of 
these plants lies in their being apt to interfere with the water supply, 
and it was for this reason that the investigations and observations 
on these plants were made. Though the number of species is not 
great the extreme rapidity with which they grow when a lake or ditch 
is neglected makes them "apt to be extremely troublesome and ex- 
pensive to get rid of. 
It is well known that to the cryptogamous aquatic flora, the 
Alga the action of copper sulphate is very deadly, and attempts 
were made to destroy these plants by the use of copper sulphate 
in sufficiently small quantities to be not deleterious to persons 
drinking the water. 
The aquatic plants which occur in the Peninsula may be divided 
into those with floating leaves. or which entirely float and those 
which are completely submerged. Those which float include the 
water lilies, Nympkea st elicit a and Barclaya motley i, an inhabitant 
only of forest streams, Limnanthemum cristatum, the Cryptocory- 
neSj which mostly inhabit the same kind of locality as the Barclaya , 
7/M 
