BOOKS AND CURRENT LITERATURE 245 



aiul leaves in potonieters were usetl in the experimentation, the tech- 

 nique of which is carefully described. 



It is a matter of common ol)servation that potatoes which have been 

 sprayed witii Bordeaux mixture exhibit a marked increase in yield and 

 in vitality over those wiiich have been unsprayed, and remain green 

 for a longer time. This is generally considered to be due to some stimu- 

 lative effect of the fungicide upon photosynthetic activity. Clinton 

 ventured the logical explanation that it is due rather to the conser- 

 vation of moisture in the, leaves by clogging up the stomata and water 

 pores with the sediment of the spray. The experiments reported in 

 the present paper show that instead of conserving the moisture in the 

 leaves the film rather facilitates water loss. A film of Bordeaux mix- 

 ture was found to cause a greater water loss than a dust covering. No 

 explanation is offered for this acceleration of transpiration, but some 

 light may be thrown on the situation from work in progress looking 

 toward the solution of the two questions which the authors raise: (1) 

 "What is a physical or chemical basis of the increased evaporation 

 from plant surfaces covered with Bordeaux mixture? (2) Is the in- 

 creased evaporation in any way related to the increased vitalit}^ and 

 longevity of sprayed leaves?" — Frederick A. Wolf. 



