MARINE ALGAL VEGETATION 43 



early in May, algae which had been frozen hard during the night, 

 apparently quite unharmed and alive when thawed, nor could one 

 perceive next day that they had suffered at all; but, as I was tra- 

 velling, I was not able to observe them more than these two days. 

 It is also a foregone conclusion that the algae left dry must freeze 

 in the winter when the cold is severe, but it does not appear that 

 they suffer thereby. 



If the cold cannot be said to have any directly injurious effect, 

 yet indirectly it may hurt the vegetation (though not to any great 

 extent) by the fact that the water freezes and the beach becomes 

 ice-covered. During severe winters a covering of ice may be found 

 during the greater part of the winter in the smaller fjords, and 

 especially where the fjord-water is abundantly mixed with fresh 

 water, and even if the winters are quite mild, yet from time to 

 time the water next the beach may freeze. In the littoral zone and 



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on rocks which are laid bare during low-tide, the ice forms in ac- 

 cordance with the substratum, and if this is uneven the ice breaks. 

 At high- water the ice-covering is lifted up; the pieces of ice may 

 then freeze together again, and break once more with the next ebb- 

 tide. During spring-tides in particular these movements are rather 

 considerable and the plant-covering may be a good deal damaged 

 thereby: but if one regards the coasts in their entirety these distur- 

 bances will prove to be of small importance. 



The drift-ice is much more dangerous to the algal vegetation 

 as the icebergs scrape the rocks with which they come in contact. 

 Strom felt, when travelling in Iceland in 1883, the year following 

 one of the years notable on account of the great quantity of ice, 

 found the littoral vegetation poorly developed in the north country. 

 This most certainly resulted from the drift-ice having blockaded the 

 coast during the whole summer of 1882. In the summer of 1898, I 

 saw on the promontory between Sey5isfjor5ur and Lo5mundarfjor5ur 

 distinct signs of the drift-ice which had been there in the spring. 

 The injurious influence of the drift-ice consists mainly in the fact 

 that it scrapes away the vegetation from the parts with which it 

 comes in contact; possibly also in the fact that it reduces the tem- 

 perature to far below normal. That the plants suddenly find them- 

 selves in a much colder medium than thev are accustomed to must 



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produce a check upon them, particularly on the more sensitive 

 species. The marine plants, however, are less affected by this than 

 the land vegetation. As a rule, ice-years occur at fairly long intervals ; 



