438 ENTOMOLOGICAL NEWS [Dec., 'lO 



the good Doctor hoping to get further light on the subject. 

 But the Doctor refused to shed any light whatever without 

 a supply of the right kind of illuminant, and Dr. E. B. Voor- 

 hees who was at that time in Europe, failed to find him at his 

 home in Wiesbaden. Meanwhile I had enlisted the aid of Dr. 

 David Fairchild of the U. S. Department of Agriculture, and 

 of Dr. N. L. Britton, Director of the Botanical Garden at 

 Bronx Park, New York City, in getting a supply of the Asolla 

 from Europe. Through the former I secured a sending from 

 the Botanical Gardens at Hamburg, which arrived in bad con- 

 dition ; through the latter I received a supply from the Botani- 

 cal Gardens at Kew, England, which arrived in excellent con- 

 dition and which was propagated in the Bronx Park houses 

 during the winter of 1909-10. It appeared also that a native 

 species of Asolla did actually occur in New ^Hrsey, but only in 

 two places where it had been planted years !^o and where it 

 had just maintained itself, without spreading, for several 

 years. 



The matter was considered worth investigating first, be- 

 cause it seemed to have German official endorsement : second, 

 because I remembered very clearly during my visit to the 

 Dutch low countries in 1900 most of the ditches were covered 

 by a complete coating of plants that parted readily for a boat 

 but closed in again, immediately behind. This vegetation, I 

 now learnt was a species of Asolla and it did not seem im- 

 probable to me that this covering of a vegetable carpet might 

 really account for the very general freedom from mosquitoes, 

 enjoyed in these regions. An attempt to secure a supply of 

 the Dutch Asolla in a nursery importation in the late winter 

 of 1909 also failed because the plants were dead when received ; 

 but from the sources already mentioned I found myself in the 

 possession, at the Bronx Park, of a small supply of plants at 

 the opening of the season of 1910. These plants were put out 

 at several points in May and at first they did well, began to 

 multiply, and apparently found something not to their liking. 

 No one could explain the difficulties so but one thing remained 



