THE M.VIUXE \\A\Jb OF (lUKHXyEY 



35 



Laurencia piiDiatiJida exists as an undergrowth from hall^ down to 

 low-tide level. 



Along tlie sub-littoral, there is a mixed assenildy of brown weeds : 

 iMJ'ncaria tuhcrculuta forms large patelies, or mingles with Lami- 

 naria saccJiarina. Ilimnufhalia lorea occurs only in colonies here 

 and there along the coast ; its best development seems to be in 

 moderately and even locally sheltered positions on rocks at about the 

 limit of low tide. A group of rocks north of tlie White Kock bears 

 an extensive crop of these plants ; at Pleinmont, which is an exposed 

 locality, it grows only in deep pools. The growth is so restricted tliat 

 a zone of the genus can hardly be said to exist. Few plants were 

 seen along the W. and N.W. coasts, and then only whei-e locally 

 sheltered, 



(c) ZONATIOX, 



The segregation of si>ecies into zones, and their arrangement at 

 different levels along the shore with regard to the tide, is the result 

 of various iniluences ; among these may be mentioned the amount of 

 insolation and desiccation that the resi>ective species require or are 

 able to withstand, and the periodic tidal exposures, rates of growth, 

 etc. These have been indicated by Eattray and by Misses S. M. 

 Baker and M. H. Bohling, who made extensive experiments and 

 jiublished valuable papers dealing with the causes of the zoning 

 of Ftici. 



Notwithstanding the mixed character of the Guernsey Marine 

 Flora, the zones or belts are distinctly traceable. They vary con- 

 siderably in width, become discontinuous and patclij^, or even dis- 

 ai)pear for some distance where climate or substratum are unfavourable 

 to their growth. The following notes deal with some of the most 

 conspicuous zones and indicate in a small measure the interesting 

 work awaiting a careful worker. 



Beginning with the Upper Littoral and descending to low water, 

 the various zones may be observed in the following sequence : — 



Upper 

 Littoral 

 Region. 



Mid- 

 Littoral 

 Region. 



Sub- 

 Littoral 

 Region. 



r Pelvetia. 



] Rividaria & Calothrix. 



I Enteromorpha. 



l^Forphyra. 



( F. spiralis. 



I F. vesiculosus. 



Fitcus. 



J Ascoj^hyllurn 

 1 nodosum. 



{^F. serratus. 

 Encrusting alga3. 

 Calcareous alga3. 

 Rhodymenia. 

 Laurencia. 

 Chondrus. 

 Encriisting algje. 

 Calcareous algte. 

 Laminaria. 



Lichens. 

 Verrucaria maura, 

 f Lichina confinis. 

 V. mucosa. 



fAscophyllum 



1 nodosum, 

 or-^ „ • 

 i' F. vesicii,- 



[^ losns. 



Lichi 



)ta pi/ipnxa. 



d 2 



