REPORT OF THE SOCIETY 73 



Spraying Results at Ottawa. 



Before giving a summary of the success achieved by various experimenters in 

 checking different species of weeds by the help of chemical sprays a few of the 

 results obtained at Ottawa may be noted. 



The weeds chiefly experimented with were wild mustard, purslane, dan- 

 delion, and Canada thistle. The chemical substances used were iron sulphate 

 (20% solution) and sodium arsenite (1 part in 250 of water). 



Plot 1. — A small plot of wild mustard in full flower with some pods forming 

 was sprayed with iron sulphate oh 24th June. On 26th June not only the leaves 

 but the whole plants were blackened and apparently dead. On 26th July some 

 shoots had grown out from the lower part of the stem and were bearing flowers and 

 young fruits. 



Plot 2. — Some purslane plants were sprayed with iron sulphate on 13th 

 July. On 20th July little or no effect was observed as a result. 



Plot 3. — A small plot of Canada thistle was sprayed on 29th -July with iron 

 sulphate. On 4th August the leaves were considerably blackened. 



Plot 4. — A small area of grass on a lawn measuring 10 by 10 feet which was 

 thickly covered with dandelions was sprayed several times during the season 

 with iron sulphate. The first spraying was on 22nd June ; on 26th June the greater 

 part of the plot was quite blackened, all the dandelion leaves and white clover 

 leaves being killed. 



On 5th July the plot was sprayed a second time and the third application was 

 made on 29th July. A few dandelion leaves had made their appearance between 

 the second and third sprayings. On 31st August there were still a few dandelions 

 surviving which were sending our fresh leaves. 



Plot 5. — Part of a path infested with weeds was sprayed with sodium arsenite 

 on 28th June. The principal weed present was Poa annua L., but there was also 

 a considerable amount of dandelion, shepherd's purse, lamb's quarters. Poly- 

 gonum aviculare L., Veronica peregrina L. On 30th June no perceptible effect had 

 been produced. 



Plot 6. — A plot of Canada thistle was sprayed with sodium arsenite on 

 29th June. On 3rd July the plants were all blackened down to the ground level. 

 White clover was all destroyed. On 26th July the thistles were sprouting again 

 at the base of the killed stem. 



Plot 7. — A considerable area under hay measuring 8 by 6 yards which was 

 badly infested with Canada thistle w^as sprayed on 8th July with rather less than 



