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 „ £ 915. 



In Indo-China. 



" Indo-China produced for export 367^ 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, Nymphea stellata and Barclaya motleyi, an inhabitant 

 only of forest streams, Limnanthemum cristatum^ the Cryptocory- 

 nes, which mostly inhabit the same kind of locality as the Barclaya y 



