Vol. XXl] ENTOMOLOGICAL NEWS 439 



to be done: visit the home of the plant and find out all about 

 it myself. In late August therefore I started and found my- 

 self at Hamburg during the early days of September. I found 

 a very cordial reception at the Botanical Institution and Gar- 

 den, at the Station fur Pflanzenschutz, and at the Institut 

 fiir Schiffs-and Tropen-krankheiten, and soon had all the in- 

 formation it was theirs to give. 



It was the Botanical Garden that had supplied the plants, 

 and the Institute for Tropical diseases that had watched and, 

 in a measure, checked the experiments made by Dr. Bartmann 

 near Wilhelmshafen and elsewhere. The records and reports 

 showed clearly enough that under favorable conditions the 

 Azolla would form a surface covering on water areas that 

 would absolutely prevent mosquito breeding and would not 

 adversely affect fish and other aquatic animals. They showed 

 also, however, and quite as conclusively that the Azolla re- 

 quired the most favorable conditions to accomplish this and 

 that even a small percentage of salt and even a moderately 

 low temperature was either fatal to the plant or checked its 

 growth. One of the New Jersey failures was thus explained 

 by the entrance of some brackish water into the pond and 

 seemed to demonstrate that on salt marsh areas or wherever 

 tides of brackish water ever entered, the plant would be use- 

 less. It was also found that a cold storm in August killed 

 so large a percentage of the plants that it required 3 weeks 

 to become re-established and, meanwhile Anopheles bred mer- 

 rily and even maintained itself along the edges where grasses 

 and rushes prevented the complete surface covering of the 

 plants. Furthermore the plants would not stand the North 

 German winters which are not as severe as our own. The 

 practical conclusion was that in North Germany Azolla could 

 not be relied upon to control mosquitoes to any practical ex- 

 tent and the experiments were abandoned. It was however in- 

 dicated that in warmer countries better results might be ob- 

 tained and experiments in the German Colonies in Africa are 

 to be continued. Curiously enough none of the officials or 



