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H. JOXSSON 



appears to have extended too high upwards, and where, when the 

 weather is calm, it is not wetted daily by the sea at and about 



V V 



neap-tide. On a warm summer's day Pelvetia can become so dry 

 in such places that, when gathered, it needs no further drying 

 the same may also be the case with Fucus spiralis. The individuals 

 of Pelvetia which grow at that height, i. e. sometimes right up in 

 the Verrucaria manra-belt, are usually very small (about 2 cm. in 

 height) and occur closely pressed to the rock; then they are often 



Fig. 3. Pelvetia canaliculata above, Fncus spiralis below. Illustration of a typical Pelveiia- 

 Fucus-spiralis-commuuity. Reykjavik, Aug. 13, 1909. (From phot, by Hesselbo.) 



found especially in crevices, and the new fronds may bear a sur- 

 prisingly close resemblance to a rosette. Lower down, where the 

 vegetation is luxuriant, the plants are about 8cm. in height. Pelvetia 

 is the smallest of the Fucacew on these coasts; it differs from the 

 others not only by its small size, but also by its lighter, yellowish- 

 brown colour, and its channelled frond, etc. The channelled frond 

 must be useful to a plant which is so exposed to the desiccating 

 action of the air as is the case with Pelvetia, because, by reason of 

 their being rolled, the under-side of the fronds is less exposed to 

 wind and weather. 



It is characteristic of the zonal division of the Fucacece on the 



