146 H. JONSSON 



well developed in E. Iceland. At an insignificant depth, where I was 

 able to see the sea-bottom, the individuals were not really closely 

 placed, but lay on the bottom, some quite flat, and others slightly 

 obliquely with the hollow surface turned upwards to the light. In 

 this way the sea-bottom was almost entirely covered by the broad 

 fronds. 



This character might be termed the calm-water character, and 

 an association-character exactly corresponding with it is found in 

 Laminaria saccharina and Fucus inflates. 



Laminaria digitata f. cucallata occurs also scattered among La- 

 minaria nigripes v. atrofulva and Alaria Pylaii. 



The Laminaria hyperborea-association. It is developed 

 luxuriantly in S. and SW. Iceland, and occurs also in E. Iceland 

 and N. Iceland, in those places which I have visited. I can pro- 

 nounce no opinion upon its general distribution in N. Iceland, as 

 dredgings have been undertaken there in a few places only; yet I 

 think that it occurs everywhere there. In E. Iceland, on the other 

 hand, where I have done a great deal of dredging, I have only 

 found it at the mouth of Berufjor5ur. It is very luxuriant in the 

 Vestmannaeyjar, forming a continuous belt round the inhabited 

 island. 



The association grows on a rocky substratum, from a depth 

 of about 4 metres to about 30 (or 40) metres, and occurs both on 

 exposed and on slightly exposed coasts; close to the limit of low- 

 tide and in water-filled depressions in the lowermost part of the 

 littoral zone small specimens may occur. In shallow water, with 

 exceptional low-tides, the upper part of the stipe is frequently seen 

 rising above the surface, raising the lower part of the frond obliquely 

 above the water. Borgesen (12, p. 755, Fig. 160) has reported and 

 illustrated this from the Fgeroes. 



In Iceland L. hyperborea does not vary in the same manner 

 as do L. saccharina and L. digitata , the fact being that it does not 

 occur in protected places, and on exposed coasts does not extend 

 so far up as the two species mentioned. Those specimens which 

 occur close to the limit of low-tide, or in pools in the littoral zone, 

 are quite as typical as the large, deep-water individuals. The asso- 

 ciation seems to thrive best at a depth of about 20 to 30 metres, 

 but on somewhat exposed coasts it also thrives fairly well at lesser 

 depths, and is then very frequently mixed with the other members 

 of the community; while at greater depths it is generally pure. As 



