104 ANNALS OF SCOTTISH NATURAL HISTORY 



latitude. 1 Indicated in S. Norway ; it occurs in Finland in 

 eleven provinces north to Kemi in lat. 65 30" (Cashen 1793, 

 Brenner iS/o).' 2 In Russia in Livonia and Petropoli (St. 

 Petersburg), etc. Thus its distribution lends itself to being 

 native in Scotland, though the greater severity of the winters 

 in 64 ' N. lat. does not count altogether, as the fall of snow 

 is greater, and this tends to the preservation of plants that 

 without it even in the south of England die in winter. 

 I am not advocating that Butomus is native in Caithness ; 

 but how do such plants become introduced (unless planted) ? 

 The appearance of semi-aquatic plants in quarries, gravel 

 pits, railway cuttings, is very curious, as they surely do not 

 occur in horse fodder, and at least in many examples of 

 Dutch and Belgium packed goods I never detected any of 

 these species. An entomological friend (Mr. Thurnel) tells 

 me that when he finds in isolated gravel pits Scirpus 

 palnstris, L., he is almost sure to find a species of moth 

 (Bactra furfurana> Haw.) whose larva feeds in the stems. If 

 it is difficult to account for the appearance of the Scirpus, it 

 seems much more so with the moth. It is easy to account 

 for the introduction of many aliens, and of many species 

 native in the south but not in the north, but semi-aquatics 

 seem to present more difficulty even than aquatics. 



C ROY DON. 



POTAMOGETON UNDULATUS, WOLFGANG, 



IN SCOTLAND. 



By ARTHUR BENNETT. 



THIS plant, which is generally considered as a hybrid 

 (Potamogeton prcelongus x crispus], was reported as a British 

 plant by Mr. Fryer 3 and by myself; 4 but Mr. Baagoe of 

 Naersted, Denmark, showed ' :> that the British plant must be 

 referred to P. perfoliatus x crispus. To this Mr. Fryer has 

 given the name x P. Cooperi, and the plate quoted below 

 and description refer to this and not to Wolfgang's plant 



1 Berlin: Skand, Halfons 1 13, 1875. 2 Hjelt : Fl. Fennica I, 513, 1895. 



3 "Journ. of Botany," t. 313, p. 289 (1891). 

 4 " Irish Naturalist," p. 124(1894). ' "Hot. liddsk," xxi. p. 221 (1897). 



