PRINCIPAL WEEDS OF CEYLON 



609 



Water weeds, scum on ponds, etc. The question of dealing 

 with aquatic weeds frequently confronts one in the tropics, and in 

 some cases involves very large expenditure of money. For sub- 

 merged weeds, removal by hand or mechanical means is the only 

 effectual way of dealing with them. Certain floating weeds may, 

 however, be destroyed by spraying with a solution of sulphate of 

 copper, say 1 Ib. sulphate to a gallon of water. The Bordeaux 

 mixture has been used with good results on weeds of this nature, 

 the solution being sprayed on the surface, if necessary repeated at 

 intervals of a few days or weeks. It has been found that if the 

 solution is not used very strong, it will not injure any fish that may 

 be in the water. A small quantity of copper sulphate placed in a 

 sack, and dragged back and fore on the surface, is sometimes success- 

 ful in destroying certain water-weeds, but experiments with this 

 method at Peradeniya did not prove effectual for such submerged 

 weeds as Hydrilhi and Limnanthemum. 



TABULAR LIST OF THE PRINCIPAL NOXIOUS 

 WEEDS OF CEYLON. 



('Indigenous to Ceylon ; t worst weeds amongst crops, etc.) 



S.=Sinhalese; r.=Tamil 



