41 



and iu Guldhorgsiind. I have also met it ia the open Baltic off Falster (in Hes- 

 uæs Bay) in 2 — 2^^ fathoms. It is of no great importance. 



4. More important is Potamogeton pecHnatus L., which iu abilit}' to stand 

 the salt water comes between Ruppia and Zannichellia. It is a larger and more 

 vigorous plant than the latter. Its pencil-thick, wliite rootstock creeps horizontally 

 in tlie bottom at a certaiu depth and ends in a pointed bud with wliich it bores 

 its way forward. From the rootstock issue erect, often meter-long shoots, which 

 are richly branched in one plane, so that they become fau-shaped. The branches 

 are supported by leaves and themselves bear leaves; these are threadlike (about 

 1 — 1,5 mm. bread), fairly stiil: and with somewhat dilated sheaths. At the end of 

 the shoot there is a many-flowered inflorescence on a thin and flabby stalk. During 

 the Howering time the inflorescence generally lies on the surface of the water, so 

 that the flowers open to the air, but after fertihzation it is lowered down into the 

 water, where the brownish fruits ripen. 



Potamogeton grows in mud-mixed sand or in jiure mud, and forms more 

 or less dense gro\\-ths, often of considerable extent. It always grows in protected 

 piaces, as for example in Ringkøbing Fjord, Albu Fjord, Roskilde Fjord, Guld- 

 borgsund and Grøusund etc. It occurs from a little beyond the low-water mark 

 (ca. 1 foot) to 2 — 3 fathoms depth. 



The fishermen do not like it, as the strong and tough shoots check the 

 progress of the seine-nets along the bottom. 



Togetiier with these brackish-water floweriug-])lants Characeæ often occur 

 in great (juautities: CJiara and allied genera (Tohipella and Lamprotliammis); 

 these will not be discussed in this paper as they do not belong to the piants 

 related to the Zostera; but they deserve a closer investigation, as, owing to their 

 extensive occurreuce, they are of practical importance to the fisheries at some 

 piaces, e. g. all along the south coast of Zealand from Faxe Bay to Skelskør. 



