KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. N:0 5. 33 



Want of light. I have already mentioned the scantiness of green algaj as a cha- 

 racteristic feature of the vegetation of the Årctic Sea proper. The speeies of this kind 

 existing there occur in very little nuinber, and are generally very, not to say extremely, 

 poorly developed, sometimes stunted to such a degree that they can hardly be recog- 

 nized. The supposition lies near at hand, that one of the causes of this state of things 

 is the want of light, the majority of the green algte beiug known to love light and to 

 prefer in general such localities where they can enjoy it in the greatest quantity. In 

 consequence of several concurrent causes, many of them cannot, on the coast of the icy 

 Polar Sea, spread themselves över the litoral zone, but are obliged to keep within the 

 sublitoral one. The quantity of light here afforded thein is certainly very slight in the 

 more northerly parts of the Arctic Sea, as compared with that which they receive for 

 instance on the coast of Scandinavia within the litoral zone. At the north coast of 

 Spitzbergen the sun is below the horizon for many months, and consequently the 

 darkness even above the surface of the sea is during a long time so deep that a 

 man cannot find his way, even at noon, without artificial light. It must be still darker, 

 of course, at the bottom of the sea, in order to reach which the scanty light would 

 have to penetrate masses of ice several feet thick, covered with a fathom of snow, and 

 besides the layer of water above the bottom. 



These masses of ice and snow are highly impervious to light, and as long as they 

 remain, only very little light gets to the bottom of the sea, even when the sun is 

 above the horizon during a longer or shorter part of the day. But the numerous Polar 

 expeditions undertaken in this century bear witness that the time is short, indeed, within 

 considerable portions of the Arctic Sea, when the sea is not more or less covered with 

 ice. On the north coast of Norway Spongomorpha arcta is met with very abundant 

 and very luxuriant, on the coast of Spitzbergen as well as in the Murman Sea and 

 the Siberian Sea it is scanty and very poor. This is the case also with other green 

 alga3, for instance Spongomorpha lanosa and Monostroma Blyttii. Other causes, such 

 as the lower temperature of the water, the want of suitable localities a. s. o. may have 

 contributed to produce this difference, and have certainly done so, but in all probability 

 the insufficient supply of light has cooperated and continues to cooperate to the same 

 effect. The quantity of light afforded, for instance on the coast of Spitzbergen, raay be 

 sufScient for these algse to live on, though it is not so large that they can attain any 

 luxuriancy of growth and form so many reproductive organs as to multiply in any 

 considerable numbers. 



K. Vet. Akatl. Handl. Bd 20. N:o .5. 



