272 Fnngiddal Properties of Certain Spray-Fluids 



Experiment 23. Disodium arsenate (containing 0-096 per cent. AsgOj). 

 On the first day (24 hours) after spraying, all the mildew-patches on all 

 the sprayed leaves were barren and apparently dead, while these on the 

 control leaves were very vigorous and densely "powdery."" By the third 

 day after spraying, the fungicidal nature of the solution was clearly 

 evident. Each spot of mildew was con.spicuous as a dead, white mycelial 

 patch. There was also a brown patch of dead leaf-cells, sometimes corre- 

 sponding in size with the area of the dead myceHum, sometimes smaller. 

 The healthy parts of the leaf showed no trace of injury. 



Exjjeriment 27 bis. Disodium arsenate (0-024 per cent. AsjOj). 



Experiment 41. Disodium arsenate (0-02 per cent. As^Og). 



Both the above solutions proved fungicidal ; no leaf -cells underlying 

 the mildew-patches were killed by the solution. 



Experiment 25. Trisodium arsenate (containing 0-077 per cent. 

 AsoOj). The fungicidal effect of the solution was clearly evident 24 hours 

 after spraying. By the third day, on some of the leaves, small brown, 

 "burnt"' patches of leaf-ceils, underlying the mildew-patches, had 

 appeared, similar to those noticed in Experiment 23 (see above). 



Experiment 20. Dicalcium arsenate (0-096 per cent. As,j05). By the 

 fourth day all the mildew-patches on the sprayed leaves were dead; 

 those on the " control " leaves (sprayed with 1 per cent, calcium caseinate) 

 were very vigorous and densely powdery. No trace of "scorching" 

 occurred on the sprayed leaves. 



Experiment 22. Dicalcium arsenate (0-048 per cent. AS2O5). On the 

 first day (24 hours) after spraying, the mildew-patches on all the sprayed 

 leaves (four) were dead — the mycelium, although still white, was com- 

 posed of hi/phae in a floccoso-collapsed condition. All the mildew-patches 

 on the "control" leaves (four), which had been left unsprayed, were very 

 vigorous and densely "powdery." 



Experiment 28. Dicalcium arsenate (0-024 per cent. AsjOg). On the 

 second day after spraying most of the mildew-patches were barren — a 

 very few patches, however, bore a few weak conidiophores at their edges. 

 The mildew-patches on the "control" leaves (unsprayed) were all very 

 vigorous and densely "powdery." By the seventh day no further growth 

 of the mildew had taken ])lace. By the thirteenth day the mildew-patches 

 were all killed; on three leaves there were small, distinct, "scorched" 

 areas of dead leaf-cells limited to the places where the mildew had 

 occurred (cf. Experiment 23). The general appearance of the sprayed 

 leaves suggested that the solution used was just fungicidal. 



Experiment 33. Dicalcium arsenate (0-01 per cent. AsgOj). The solu- 



