NOTES ON PONDWEEDS. 189 



A specimen which Dr. Tiselius has also sent me, named by him 

 "P. salicifolius Wolf." (and of which he says, " Haec planta 

 omnino est congruens cum speciminibus orig. a Wolfgang in fluvio 

 Vilia prope Wilnam lectis "), is very like the early state of a form 

 of P. decipiens from the Warwick Canal, kindly sent to me by Mr. 

 H. Bromwich. This latter plant was distributed by the Exchange 

 Club as " P. decipiens var. affined It differs in some respects from 

 the type of Nolte,* but may, I think, be placed under P. decipiens. 

 Here also I would place a plant, distributed by the Rev. Augustin 

 Ley, and named " P. salicifolius Wolfg." in Lond. Catalogue, ed. 

 viii. I need hardly say that I am not in any way founding my 

 estimate of the specific states of the Herefordshire plant on Dr. 

 Tiselius's notes ; I formed my opinion of the position of the Here- 

 fordshire plant on quite independent grounds. Indeed, I have not 

 sufficient knowledge of the specimens and writings of the great 

 European botanists who have written on the genus Potamogeton 

 to enable me to give an opinion as to whether the plants of Wolf- 

 gang and Nolte are referable to the same specific aggregate. 



Through the kindness of Professor Babington, I have been able 

 to examine carefully and repeatedly his unique specimen of " P. 

 Imujifolius,'" and I have come to the conclusion that it is certainly a 

 decipiens-form, but one that is decidedly more towards lucens than 

 any other I have seen. While the leaf-structure is that of decipiens, 

 the peduncle and flower- spike are like those of lucens, but the flowers 

 seem imperfect, and suggest that they are barren. 



It may perhaps be possible for P. decipiens to be fertilised by the 

 pollen of other species ; but in the fens, at least, it never produces any 

 pollen of its own whatever, the anthers being quite empty. In spite 

 of this the flower-spikes are visited by insects and may rarely 

 become fertilised. I am not aware that any author has pretended to 

 describe the fruit of P. decipiens, although almost all have carefully 

 described the hitherto unseen fruit of P. nitens ! P. decipiens is 

 one of the most beautiful species known, almost equalling P. prm- 

 loiujus in the colour and delicacy of its leaves. In warm summers 

 it flowers freely, and the drupelets swell for a short time and give 

 promise of maturity which is not fulfilled. It is rather common 

 in the Cambridgeshire fens around Chatteris, but I have met with 

 one patch of it only in Huntingdonshire, just within the border of 

 the county at Earith. 



Although we must almost certainly regard this plant as a hybrid, 

 I am in favour of retaining the specific name of Nolte, at all 

 events until its rank is definitely settled by actual experiment in 

 cross-breeding, or by more complete observation in the field. Possibly 

 many " species" of fertile Potamogetons are of hybrid origin; but 

 this note is already too long, so I must reserve any further remarks 

 on this subject for a subsequent paper. 



* I have Mr. Bronrwich's plant under cultivation, and hope to make it the 

 subject of a subsequent note when more fully observed. 



