76 SOME ADDITIONS TO THE DORSET FLORA. 



cuneate at tlie base, and more regularly serrate. My specimen was 

 gathered two years ago and rightly named at the time, though I 

 did not till lately realise that this sub-species (as Symc considered 

 it) was only on record for Moray and Denbigh. It is probably not 

 indigenous in either of these localities any more than in Wallis 

 Down, near Bournemouth, where I found my specimen, on ground 

 that was formerly part of the heath ; but, like many other corn- 

 field weeds that seem quite at home now, it was probe bly introduced 

 at some time or other with foreign seed. 



i\Iy next plant is a Pond-weed, Avhich is given in the London 

 Catalogue (8th Ed.) as a species, 1490, Pofamogeton decipiens* In 

 the 7th Edition it was given as u variety of P. lucens. In Bab. 

 Man. it stands as a species ; in Hooker's Student's Flora as a sub- 

 species under P. lucens. As a matter of fact it is none of these, 

 but a hybrid betAveen P. hicens^ to which it bears a good deal of 

 resemblance, and P, perfoliatus, two of the commonest species in 

 our rivers. It may easily be distinguished from the former by the 

 sessile leaves, and from the latter by the much longer leaves which 

 do not clasp the stem. It occurs in the K. Frome above "Wareliam, 

 a little to the west of the railway bridge, where the Swanage line 

 crosses the river. There was no sign of it in the R. Piddle at 

 Wareliam, though both parents grew frequently together. The 

 Dorset plants seemed to be fruiting fairly well, but from the way 

 in which the fruits have shrunk in drying I doubt if they were 

 effectually fertilised, or would have had any vitality. It is, of 

 course, usual with hybrids for the seeds to be more or less imper- 

 fect ; sometimes the ovules show no development ; more commonly 

 there is an apparent maturing of the ovules to a greater or less 

 extent ; and this is what had taken place in the Wareham Pond- 

 weed. In some other examples of P. decipiens, e.g., specimens I 

 once gathered in the canal at Navan, and specimens brought me 

 this last summer by the Rev. R. P. Murray from a canal near Bath, 



* After this i>aper was written tlie President of the Society informed 

 nie that he had previously observed this Pond-weed in the K. Stour,-- 

 E. F. L. 



