148 BIOLOGICAL PROBLEMS 



combating mildew, and usually with little success. 

 This is not surprising, since the liquid possesses a 

 low wetting power, and when applied to plants with 

 shiny foliage, such as Wichuraiana roses, or covered 

 with a waxy coat, as in the case of carnations, it rolls 

 off in droplets. Moreover, owing to the physical 

 characters of the felt-like mycelial skin formed on the 

 plants by such fungi as the American gooseberry 

 mildew and rose mildew, the mixture does not wet 

 the fungus, and hence does not penetrate nor kill. 

 But add a soap, and the efficiency is at once increased 

 through the improved wetting power. Soapy mix- 

 tures in which the amount of liver of sulphur is 

 reduced to 4- ounce per gallon have given results 

 equal to those obtained when using a J-ounce-per- 

 gallon solution in water. The wetting power of 

 Burgundy mixture can be considerably increased by 

 adding milk or soap powder. One-quarter and one- 

 half per cent soap- Burgundy will not only prevent 

 trys appearance of the American gooseberry mildew, 

 but kill the perithecia without bringing about the de- 

 foliation caused by using stronger solutions. If we 

 can reduce the strength of Burgundy mixture, a con- 

 siderable economy in chemicals is effected; against 

 the economy in chemicals must be set the cost of the 

 soap, but it should not be difficult to find an inexpen- 

 sive soap, which would bring down the cost of the 

 mixture. 



Burgundy mixture can be modified to suit different 

 needs. A 2-per-cent solution once applied in Feb- 

 ruary will prevent peach-leaf curl due to Exoascus 

 deformans\ a i-per-cent solution will stop leaf-spot 

 of celery due to Septoria Petroselini; a i-per-cent 

 lacto-Burgundy will check carnation rust; a ^-per- 

 cent soap-Burgundy will prevent delphinium mildew 

 without disfiguring the flowers. Other special mix- 



