THE MARINE ALCKE OY (JUEttNSEY 37 



Forphyra Zone. 

 Thin, even patchy at places, and abnormall}' wide in others, the 

 zone is more or less continuous round the island, sometimes the line is 

 so narrow as to consist of single plants. The poorest development 

 seems to be in exposed localities, where the plants are umbdical m 

 form, short and tuft;ed, and occur mostly as a scattered undergrowth 

 among F. spiralis and Enteromorpha spp. With semi-exposure the 

 zone mcreases in width and takes a lower range. The growth is 

 generally very unequal, and frequently mingled with F. vestculosus. 

 On one side of Lihou Causeway it measured 2 feet; at Cobo, 

 Albecq, and along the north arm of Rocquaine Bay there are large 

 patches 13 feet across. Increased shelter produces larger plants of more 

 continuous growth, as at L' Ancresse Bajs where there is a broad band 

 of the species several feet wide along the mid-littoral. A remarkable 

 case is seen at Petit Bot in extreme shelter : the principal feature is 

 a prolific growth of Forphyra down one side of the Bay which 

 mingles at first with F. spiralis and Enteromorpla spp., and 

 descends through the zone of F. vesiculosus to low-water mark. 

 The plants here are of considerable size, laciniate in form on low 

 rocks, but umbilicate on boulders. 



Mid- LITTORAL. 



The Fiicus Zone. 



Fucus spiralis is very sensitive to climate. In exposed localities 

 it is found only in chinks of the rocks, more especially choosing those 

 which run parallel to the shore, the band therefore is patchy and dis- 

 continuous. With semi-exposure F. spiralis begins among the 

 Felvetia and then forms a well-marked belt about 5 or G feet wide. 

 Where the beach is pebbly and the rocks are low, F. spiralis grows 

 over them, but if the shore is very rough and composed of sharp, 

 high-standing rocks, with deep clefts, this species is absent. With a 

 little local shelter, F. spiralis develops into the var. platycarpus, 

 particularly on the sheltered sides of boulders ; the fronds are often 

 as much as six inches in length. r n • 



There is besides an abundant undergrowth ot the tollowmg 

 species '.—Geramium ruhruWy Spermothamnion Tumeric Cladophora 

 rupestris, Bhodochorton Bothii, Catenella repens, Fnteromorpha 

 intestinalis, Ectocarpus littoralis, Rildenhramltiaprototypus, si^ore- 

 lino-s of Fiociis spp., Ascophyllum nodosum, and Cladostephus spp. 



""f. vesiculosus occure about half tide on low rocks and stones : 

 it appears either above or below Ascophyllum nodosum, according to 

 the nature of the rocks (see p. 38). It may ascend up into the 

 F. spiralis band, or descend and mingle with F. serratus. In mode- 

 rately exposed districts, as at Cobo, F. vesiculosus sometimes takes 

 the place of F. serratus and extends down to the limit of low tide ; 

 the line is then rather wide, ill-defined, and sparse. The greatest 

 development is in sheltered situations. The epiphytes of this species 

 are — Folysiphoniafastigiata and Fylaiella littoralis. The tollow- 

 ino- plants frequently occur as undergrowths:— i?Ao(/;/w^«7« palmata, 

 Cfadosteplius spp., Chondrus crispus, and Lithothamnton Lenormandi. 



