344 . MR. H. B. GUPPY OX THE THAMES 



or pond-mud in which the bird sought its food ; and I cannot 

 help thinking that wild ducks and their kindred, when straining 

 the mud, must often swallow the seeds or seed-vessels of the 

 numerous water-plants that are not represented in the Thames 

 drift, and w^hich, by experiment, we learn have little or no 

 buoyancy in water. In the favourite haunts of these birds, 

 abroad and at home, an investigator might, without much trouble, 

 carry out this inquiry ; yet in the birds sent from many parts of 

 the world to our London markets we have by no means a limited 

 field of research. 



There are one or two miscellaneous matters concerning the 

 Thames drift to which I will refer in concluding this paper. They 

 are concerned rather w T ith particular plants than with the general 

 principles of dispersal. 



Not the least interesting things that I found floating in the 

 Thames in March were a few buds of Hydrocharis Morsus- 

 ranee from which I am now raising plants ; and I will take 

 this opportunity of giving in a very few words the results of 

 numerous observations and experiments on a plant to which I 

 was especially attracted by reason of its wide distribution. It 

 is, I think, well known that in this climate it propagates itself 

 rather by buds than by seeds. I had great difficulty in getting 

 any seeds from plants in my greenhouse, or in the lakes and 

 ponds of Epping Forest, and none have yet germinated. Many 

 of these buds float through the winter from the autumn to the 

 spring, when they expand or, to put it more accurately, throw 

 down their leaves and develop into the characteristic plant. I 

 have now plants growing from buds I have kept floating from the 

 autumn to the spring, plants growing from buds found floating 

 in the Wanstead lakes in the middle of December and in the 

 Thames in March, plants growing from buds that were inclosed 

 some weeks in ice, and plants growing from buds that sank after 

 floating a week or ten days in sea- water, which is the limit 01 

 their flotation in the sea. Thinking these hardy little buds were 

 capable of a great deal more, I tried the effects of some months 

 of drying ; but as yet they have failed to respond. It is scarcely 

 likely, however, that the plant was introduced into this country 

 as a bud. The seeds Bink in fresh water and sea-water ; but one 

 could hardly regard them as able to withstand a bird's digestion. 

 When the fruit bursts, the gelatinous pulp containing the seeds 

 is discharged, part of which sinks slowly whilst some of it adheres 



