179 



Potamogetonaceæ. 



Determ. J. Baagøe, Næstved, Denmark. 



I. Potamogeton. 



1. P. nodosus Poir. F. fluitans Roth. 



Roth's name is from 1788 and elder than Poiret's name, which 



is from 1816; I have used the latter '), because some botanists consider 



the steril hybrid P. lucens x natans as Roth's plant, others the 



fructiferous and again others (Aschersou und Graebner Syn. Mitteleur. 



Flora 1897) refer both the hybrid and the fructiferous „P.ßuilans''' 



to the same species. This is not at all correct, these two forms 



diverge in several respects. Original fructiferous specimens of Roth's 



P. fluitans I have seen iu the herbarium of St. Petersburg, but Roth 



has in his describing the plant iu Tent. Fl. Germ. I. (1788) 72 



„. . . . foliis inferioribus lougissimis" and in Tent. Fl. Germ. II 



(1789) 202 „ folia inferiora pedalia et longiora" no doubt 



had the hybrid before him (the above mentioned character is parti- 



culary characteristic for the hybrid, while the fructiferous plant 



has short submerged leaves); perhaps Roth has emitted both plants 



under the same name, and until it can be fixed, which plant shall 



bear Roth's name, or whether this is to be retained after all, I 



will use the name given by the author, who is next after him, 



viz. P. nodosus Poir. (P. occidentalis Sieb., P. canariensis Link, 



P. americanus Cham, and more are of later date). 



N. 1951. Chiwa, in a pond. July 11. 1899. 



N. 1980. Chiwa, iu a pond by Chasawat. July 15. 1899. 



M Proposed by Mr. 0. Hagstrüm (Lyswik, Sweden). 



12^ 



