742 



for each species. He further writes: (5, p. 414) »In den beschat- 

 telen Grotten, in welchen Lithophijllum Lenormandi, Callithamnion 

 elegans, Derbesia Lamourouxii die åussersten Grenzen der Vegetation 

 bezeichnen, verschwinden diese Formen schon voUståndig in ge- 

 ringen Entfernungen vom Eingange. Ist es erlaubt aus den Befunden 

 an der Oberflåche auf das Verhalten in grosseren Tiefe zu schliessen 

 — die Berechtigung dazu diirfte kaum bestritlen werden konnen, 

 denn die Algenformen sind an den entsprechenden Ortlichkeiten 

 theils ganz dieselben, theils nahe verwandt — , so muss die Licht- 

 intensitåt auch hier bei vorhandenem Pflanzenwuchs noch eine 

 ziemlich betråchtliche sein«. If it were possible to measure in some 

 way the amount of light that reaches the algæ growing in the inner- 

 most parts of the caves, this might certainly, as suggested by 

 Bert hold, serve as a measure of the intensity of the light at the 

 depth where the algæ-vegetation disappears^ 



b. Sheltered Coasts. 

 Th e Ch lorophyceæ-Form a tion . 



Here this formation is chiefly represented by an Enteromorpha- 

 association, but sometimes we also find others of the different asso- 

 ciations belonging to this formation on exposed coasts e. g. the 

 Prasiola stipitata-associaiion. 



The E nteromor pha-association grows highest, often somewhat far 

 above the highest water mark and stretches down to a little be- 

 low it. It is often found on moist rocks and in clefts and cracks, 

 where fresh water oozes from the rock, and consequently it does 

 not form any continuous belt, but larger or smaller patches in these 

 piaces. It may moreover be found at the inner end of bays and in- 

 lets, where the bottom is covered with gravel or stones, and here 

 it may often partly replace the Fucacece- formation. It is, for in- 

 stance, richly developed in the innermost part of Kaibak- and Kolle- 

 fjord, in Skaalefjord elc. Different forms of Enteromorpha intestinalis 



^ In order to try if any result might possibly be obtained, I used in 1900 

 Wynne's actinometer, which serves for photographic purposes to indicate the 

 exact term of exposure in a certain place (cf. Joh s. Schmidt: Uidrag til Kend- 

 skabet om Skuddene hos den gamle Verdens Mangrovetræer, København 1903, p. 11). 

 But in these caves, where the liglit is faint and the term of exposure consequently 

 long, the instrument proved less useful. With an in.strument constructed by Dr. 

 Steenstrup (cf. Meddelelser om Grønland. 25, page 1) to measure the intensity 

 of the light, a satisfactory result might possibly be obtained. 



