30 THE MARINE ALR.E Or (UERNSET 



high. Results of experiinents made by Dickson between Bolt Head 

 and Beny Head at depths varying from 80 to 17 fathoms show that 

 1 kilcgram of sea-water contains 19-41 to 19-31 grammes of chlorine: 

 "the w^ater of the English Channel as far east as a line joining the 

 Isle of Wight and Cherbourg is constant in composition at different 

 seasons of the year/' One may therefore safely conclude that these 

 figures indicate fairly correctly the degree of salinity for the waters 

 bathing the Channel Islands. It is not, how'cyer, so much the amount 

 of salinity wdiich aft'ects the growth of seaweeds as changes in its 

 deg)"ee which is harmful to them. 



On the other hand, almost every creek has its little stream of fresh 

 water running down it; certain species, such as GraicloKpia jiUcina, 

 are to be found in localities where the water is clear and flowing 

 quickly. Zosfera beds also tloui'ish in the neighbourhood (;f fresh 

 water among mud and sand ; upon their leaves and stalks are found 

 many epiphytic Algie. Ulvas, Enteromorphas, and even Porphyras 

 are unaft'ected by the presence of streams, and the tw^o former abound 

 in brackish pools where rain-water is conserved. 



At Pulias, on the north-west coast, there is a large brackish pool ; 

 formerly CJadopliora jlavescens and CI. fracia were to be found 

 there. In 1911 and 1912, I found Calotlirix Crustacea, Lynghya 

 semi plena, Clicetomorplia Union, PFingsheimia scutafa, Entero- 

 mo)pha prolifera, 'AU(\. GayelJa polyrhiza, but in 1914 only Chceto- 

 morpha linum, E. infesfinalis, and E. compressa, so that the nature 

 of the pool seems to have changed. 



Val du Braye is a neck of land between L'Ancresse and St. Samp 

 son's which has been reclaimed from the sea ; it contains a brackish 

 pool where marine alga' have been said to exist. I was unable to 

 obtain access to it. 



Many of the fields lying along the shores of the west and north 

 coasts are Hooded in winter b}^ the sea, and one w^ould expect to find 

 some salt-marsh forms of Algse, but I never succeeded in doing so. 



All available ground which is not built on or under cultivation is 

 utilized for grazing purposes, and the soil becomes highly charged 

 with manure, etc. This has perha})s gradually effected the extinction 

 of marine algie in the above pools and fields ; it is certainly the case 

 with the Pulias Pool. Marquand alludes to this as a possible explana- 

 tion of the paucity of fresh- water algie. 



Along the upper limits of the shore, such as the bases of cliffs etc., 

 the following fresh-water algie are often found mingling with the 

 habitants of brackish conditions : — 



CiiLOROPHYCE.i;. Pleurococciis vulgaris Meneg. ; GJoeocystis 

 rupestris Rab. [on moist rocks at the foot of the cliffs, Petit 

 Port] ; Porphyridium crueritum Nag, on earthy cliffs at Pleinmont ; 

 Vaucheria sessilis Vauch. [Moulin Huet Valley]. 



Phycochromophvce.e. Chroococcus turyidus Nag. [M.] : 

 Glop.ocapsa granosa Kiitz. ; Microcystis sp. ; Merispomedia glauca 

 Kiitz. [M.] ; Nostoc commune Vauch. [M.] ; Oscillaria tener- 

 rima Kiitz. [at base of the cliffs] ; O. limosa Libert [roadside ditch 

 near St. Sampson's bridge] ; Rivularia yranulifera Carm. [at base 

 of the cliffs, Petit Port]. ' 



