(3) — 95 — 



most unlikely conditions of depth of water, raud, or 

 dried mud never produces them. Every spécimen of so called 

 lucens wilh fioating leaves I hâve seen are referable to P. angiisti- 

 folias Bertch et Presl (P. Zizii Roth). Now M. Raunkaier 

 places P. lucens withP heterophyllus Schreb. : tue latter will grow 

 with no water, even among grass that bas been eut for hay ! That 

 is by their anatoinical structure. Of course it raust be remem- 

 bered bis work is only preparatory, and he may bave to alter 

 some groups as be observes. 



This differs for P. lucens by being in ail its parts a sinaller 

 plant, by the nervation of tbe leaves, by the dark color of ail 

 its parts (like that of P. longifolius Gay), shorter peduncles, 

 and spikes. 



Two spécimens are contained in the Herbarium from Mada- 

 gascar, it also occurs in Bourbon ! Mauritius ! 



3. P. lucens L. 



The following remarks refer to spécimens in the herbarium, 

 that are named in accordance with thèse remarks. 



The african spécimens of the genus named P. lucens and 

 P. lucens var., are often so fragmentary, as to make it impossible 

 to speak with certainty, whether referable to P. lucens or to 

 P. Schiveinfurthii Ar. Benn. in FL trop. Africa VIII, 220, 1901. 



Three of the sheets in the Herbariim I think are my 

 P. Schiveinfurthii. Great help will be afïorded by the excellent 

 work begun by C. Raunkiser \ when ail the species can be so 

 studied : the difficulty is to get material. 



I am inclined (though the sp. I possess is very poor) to refer the 

 P. capensis Scheele in herb. Buchenau to P. Schiveinfurthii, but 

 cannot see that Scheele ever published bis work, though he sent 

 Buchenau a Clavis of the species. The label on my spécimen 

 reads : « P. capensis mihi 



Uitenhage. 



July. leg Zeyher. » 

 « Ex herb. Scheelii qui schedulam scrip. » 



One thing is certain P. capensis Scheele ms. is not P. Thun- 

 bergii Cham. as the original type in the Berlin Herbarium 



1 Anatomical Potamogeton-Studies etc. Bot. Tidsck. XXV, 3, 253, 1903. 



