314 TRANSACTIONS OF THE [Sess. lxxxiii 



tion or non-serration of the leaves in the lucens group ; but 

 in deciiAens, Xolte (by this method made into two hybrids 

 by Graebner, I.e.), the serration is not constant, due in some 

 cases to age ; in others the early leaves are not so, later 

 ones are so, as I have proved by testing dozens of specimens 

 under the microscope. With these specimens Mr. Chester 

 sent others that seem to me to be a hybrid with jper- 

 foliatus, Linn. 



With regard to Wolfgang's description of the leaves, 

 '■ margine crispatis," this is not shown on his specimens, 

 but perhaps is only apparent when living. Then the 

 stipules, " stipulis magnis, elongatis, obtusicaulis," in the 

 majority of specimens this holds good, but in one of 

 Besser's the upper ones are decidedly acute. In the Vienna 

 herbarium there is a specimen from " Oregon, U.S.A., Lyall, 

 1861, Boundar^T- Commission." This in 1892 I referred to 

 Gay's plant, but now I would not be sure ; it may not be 

 the elongated form of lucens but perhaps the /. insigne, 

 Tiselius. The P. longifoliua, Gay of Babington, Eng. 

 Botany, supp. t. 2847 (1840), is not the plant of Gay, but 

 I believe a hybrid. I have named it in Jour. Bot., xxxii, 

 204 (1894), P. Babingto7iii = P. lucens x praelongus. It is 

 usually stated that onl}^ one specimen was gathered in 

 Lough Corrib in 1835 by Mr. J. Ball ; this is not so. Two 

 were gathered, one sent in the fresh state to Pi-ofessor 

 Babington, and one retained by Mr. Ball. Its history may 

 be summarised as under : Babington in 1840 considered it 

 Gay's plant ; Hooker and Arnott in 1860 was undecided 

 where to refer it ; Syme in Eng. Botany thought at first 

 it might be praelo'jtgus ; Hooker's Students' Flora, ed. 3 

 (1884), rather contradicts itself ; Fryer in 1890 placed it 

 under decipiens, Nolte, but does not notice it in Potamo- 

 getons of the British Isles ; and the Messrs. Groves in the 

 9th edition of Babington's Manual retain the account of 

 the 8th edition and add Fryer's and Bennett's opinions. 



