160 THE .idl'liXAL OF BOTANY 



No. 5 definitely rejects numerous names whose validity under the 

 International Rules is very doubtful, and which are in any case 

 superfluous. 



If No. 8 were adopted, lists of nomina conservanda would command 

 more respect; at present they are apt to he regarded as arbitrary. 



The acceptance of No. 11 would lead to a great saving of time. 



Finally, the adoption of Nos. 1 and 6 would prepare the way for 

 that world-wide agreement on plant nomenclature which must he the 

 aim of all who have the progress of systematic botany at heart. 



[We shall be glad to publish comments on Mr. Sprague's paper. 

 or to publish further suggestions. With regard to no. 11, the paucity 

 of examples of the use of a small initial letter for proper names may 

 be noted, as also the fact that the practice, temporaril} r adopted at 

 KeWj has since been abandoned there. — En. Journ. Box.] 



POTAMOGETON IN THE ENGLISH LAKES. 

 By W. H. Pearsall and W. H. Pearsall, M.Sc, F.L.S. 



In examining the aquatic vegetation of the English Lakes, the 

 authors have been much struck by the great variability shown by 

 the genus Potamogeton. In many cases, the species observed in 

 nature showed an obvious relation to the environmental conditions 

 under which they grew, and it was often a matter of some difficulty 

 to decide whether the differences observed in the various species were 

 simply form variations due to the environmental conditions, or dis- 

 tinct characters having no necessary relation to the environment. 

 In the former case, alteration of the environmental conditions toward 

 the normal would be followed by modification of the characters 

 of the plant under observation, giving it a more typical form. In 

 the second case — on the other hand — the variations observed would 

 not be lost on alteration of the habitat conditions. 



In addition to the consideration of such cases of observed varia- 

 tion, it is proposed to enumerate the species of Potamogeton found in 

 the English Lake District, and to summarize their distribution. 



The pusillus section of the genus Potamogeton is divided by 

 Hagstrom in his " Critical Researches on the Potamogetons " 

 (Kungl. Svenska Yetenskapsakademiens Handl. Bd. 55, 1916) into the 

 two groups : — 



I. PusiLLl CONNATI : P. rutilus, P. mucronatus, and P. panor- 

 mitanus. 



II. Pusilxi conyoluti : P. obtusifolius, P. SturrocMi, P. 

 pwsillus, and P. franconicus. 



Of these species, P. rutilus, P. mucronatus, P. Sturrochii, and 

 P. franconicus have not been yet found in this district, although 

 occurring in other parts of Britain. 



Potamogeton panormitanis Bivona Bernardi. Nuove piante 

 inedite, Palermo, 1838, 6-7. P. gracilis Fries. Novit. Fl. Suec. 

 1828, 50. P. Noltei Ar. Benn. in Journ. Bot. 1 S00, 300. 



This species has long been confused with P. pusillus or treated 





