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Chamisso (Linnsea 2, 1827) figures no fruit of his P. masca- 

 rensis, and as there is no fruit on the original spécimen in tke 

 Berlin Herbarium, we are unable to compare it with his 

 P. americanus. This spécimen is certainly not P. natans L. !, 

 and it is again perhaps an endémie form of P americanus 

 characterised by the great development of the central and 

 4 primary nerves which stand up above the surface of the 

 leaf, while the secondary ones are immersed in the leaf. In a 

 note on the Berlin example (itself very poor) I hâve said « I am 

 inclined to refer this to my P. Cheesmanii)), but it is really 

 impossible to deal with such poor spécimens in this group of 

 the genus. 



« Plants of Yellowstone Nat. Park, n° 6771. Pot. lonchites 

 Tuck. Madison river. Nelson. » 



This peculiar state of P. americanus is exactly the same as 

 some spécimens of Iiugel from Florida which I possess. 



5. P. angustifolius Bertch and Presl. Eostlin 2, 19, 13, 

 1821 — P Zizii Mert. and Koch ap. Chamisso Linnœa 2, 202, 

 1827. 



This part of the Linnsea was published on April l st so it 

 précèdes Roth's Enum. Plant. Germ. 1, 581, 1827. Chamisso 

 says « M. et K. in litt. » 



Most authors refer to the 3 éd. of Rôhling's Dent. Flora. I, 

 845, 1823, but Mert. and Koch there name the plant as P hetero- 

 pHyllus S laïifoliiis, P Zizii only occurving in the index. 



Not only that, but Koch after the publication of the l st volume, 

 i. e. in 1824, sent to De Candolle's Herbarium, a set of the 

 Potamogeton of the Dents. Flora, among them two spécimens 

 of the above plant, named : 



« P. heterophi/llus 8 latifolius fi. nostr. e. Palatine », so he still 

 in 1824 retains the Dent. FI. name as a variety. 



It is true that Meyer Oh. Eannov. 521, 1836 refers to « P. Zizii, 

 Ziz et Koch Cat. Pal. 1814»; but I can find no such a name 

 in that Catalogue, at least not in the British Muséum copy. 



Again Koch in the 2 nd. éd. of his Synop. FL Germ. et Helv. 

 2, 778, 1844 calls it « P gramineus L. y Zizii » quoting the 

 Dent. FI. under the heterophyllus variety. 



So I maintain that by writing « P Zizii M. et K. Dent. 



