82 THE JOl'KNAL OV IJOTAM' 



many stations is exti-aordinary and raises an interesting question. In 

 several of these localities the plant may have existed from time 

 immemorial and have been simpl}^ overlooked. But in one pond at 

 least those who have explored the district with some care are positive 

 that it vfus not present a few years ago, and that being so, how is the 

 extension of the plant to be accounted for ? Miss Roper has ven- 

 tured the suggestion that movements of waterfowl, wild duck in 

 particvilar, might enable it to occupy new stations. The suggestion 

 was scouted, but to my mind it is quite reasonable. For it is obvious 

 that if a stick will withdraw from the water a number of adherent 

 organisms no duck could swim in it and depart without carrying them 

 off in quantity upon its feet. Duck are plentiful in our North 

 Somerset lowlands. In 1873 or 1874 Mr. Hewett Watson collected 

 WoJjfia from a pond near Thames Ditton, where he had botanized for 

 forty years, and no one who knew him could believe that he had so 

 long overlooked it. G. F. Scott Elliot, discussing the range-limits of 

 plant species (Trans. Nat. Hist. Soc. Glasgow, 1898) attributes the 

 wide distribution of freshwater plants to the migration of birds. He 

 says, for example, that taking the extremely long range of ducks into 

 consideration, it is conceivable that a freshwater plant might pass 

 right round the globe in four seasons. The supporting evidence of 

 Darwin and other observers might be quoted, but an article by the 

 Kev. E. A. Woodruffe Peacock on " Wild Duck Carriage " in the 

 Selborne Magazine of last July should suffice to remove whatever 

 dovibt may be entertained on the cogency of this theory. If such a 

 mode of dispersal be operative in the marshlands of North Somerset, 

 we may naturally look forward to a continued spread of Wolffia 

 among our outlying ditches and ponds. 



Lemna trisiilca L. Several fronds in flower of this and of 

 L. jJoh/rrliiza were brought from the Glastonbury peat moor by 

 Mrs. Sandwith. 



Potamoc/eton Dntcei Fryer. New to Bristol and to Somerset. 

 First gathered in the Avon at Saltford, August 1916, by Mr. Bucknall 

 in company with Mrs. Wedgwood, who afterv.'ards suggested that it 

 agi-eed with the description of P. Drucei. In July 1917 several 

 large patches of the plant were seen between Kelston and Saltford 

 Locks. These had well-developed broad floating leaves, as well as long- 

 ]5etioled lanceolate submerged ones. In August the broad leaves were 

 still more abundant, while the others had nearl}-^ disappeared. Mr. Druce, 

 himself, on seeing the 1916 specimens, at once agreed to the name 

 P. Drucei ; and Mr. Bennett, after examining a complete series, 

 said there could be little doubt they were Druce's plant. In view of 

 the opinions of Fryer and Hagstrom that P. Drucei may be the 

 hybrid alpiniisy.natans, it must be noted that the Avon specimens 

 do not show the red colour stated to be present in the Loddon plant, 

 and that P. alpimts has not yet been met with in the Avon. Mr. 

 Bucknall could not find any fruit or flower. 



P. piisiUits L. Detected (1915) by Miss Roper in the artificial 

 lake at Eastville Park, G., supplied with water from the River Frome. 

 This, therefore, may be regarded as a confirmation of Dr. Thwaites's 



