72 PBOCEEDIKGS OF THE 



Societies of Natural Science of the British Association asking for 

 iiitormation on the subject. 



To this, as may be seen, numerous replies were received and 

 much valuable iiitormation obtained, for which the writer now 

 heartily thanks all hi.s correspondents. One unavoidable defect 

 in the scheme consists in the fact that the period of maximum 

 abundance having begun about 1852 (in the Lincolnshire Fens, 

 the river Cam, &c.), there would be iew botanists whose memories 

 Avould extend iar enough back to be able to compare the present 

 M ith the past. But, with due allowance for this, the indications 

 are that on the whole the plant is not now so abundant as to be 

 a nuisance but has generally established itself as a denizen It is 

 however, i)robable that there are waters to which it has not vet 

 penetrated and in which it may still flourish as in previous years 

 Such may be the case with the artificial water of Monlton 

 Grange, Northants, where Mr. H. N. Dixon, Hon. Sec. Xorthants 

 JNat. iiist. boc, describes it as "a great pest." It would be 

 interesting to know whether it has ever re-appeared in water 

 where it has flourished and died out, as might conceivably happen 

 after a lapse of time sufficient for the bottom to recuperate If 

 It has not done so anywhere, it would not be unreasonable to 

 attribute it to a diminution of the vitality of the species as 

 suggested above. 



The following reports from different Counties from the south 

 of England to Banffshire are probably sufficiently representative 

 of the whole of Great Britain. 



Devoxshire. 



Mr. J.L. Sager, M.A., on behalf of the Exeter University 

 College Field Club, writes: "It occurs in more or less 

 abundance in the Rivers Exe, Culm, and the Exeter Canal It 

 has been known to flower occasionally, but fruits have not been 

 seen," 



Mr. H. J. Morgan, a member of the above Society, says that for 

 some time before 1878, "the right bank of the Exe from the 

 Bridge to the Gas Works (over 200 yds.) was one thick mass of 

 Elodea. Since that date this plant has become by no means 

 plentiful in this place. Many ditches on Exminster Marshes were 

 almost filled with Elodea about seven vears ago. There is certainly 

 not so much there now." ' 



Dorsetshire. 



Mr. N. M. Eichardson, President Dorset Field Club, reports • 

 " Mr. Filleul says he sees it in every stream he fishes, but our 

 own native weeds far more than hold their own against it " 



Mansell-Pleydell, 'Flora of Dorset,' 1874 : " Str^'eams anil ponds 

 common ; thoroughly established, becoming a most troublesome 

 plant." 



