62 Grevilte*s AHgce Brit&nnicd*, 



low and high water-marks, living an amphibious sort of life, 

 alternately exposed to the atmosphere, arid covered by the 

 tide. The t/lvse and Porpbyrae intermix with them, and 

 give some variety to the shore by their greeri ' ^rid j>urple 

 fronds. The Laminariese oceupy a lower icitit?, ' fdi* they are 

 strictly aquatic, and choose, therefoi^, k statioti nOt liable to 

 be left dry at the reflux of the tide. With the ejiception of 

 L. debilis and latifolia, the others are widely and generally 

 distributed along our coasts, affording shade and shelter to 

 myi'iads of creeping things, and becoming ultimately a source 

 of profit to the agriculturist, to whom the " alga projecta 

 vilior " is an unintelligible comparison. The other families 

 may be considered as subordinate ; for, aithough maiiy genera 

 and species amongst them, as, for example, Chordaria, Fur- 

 cellaria, Desmardst/a aculeata, &c., ai'e met mth abundantly 

 everywhere;, and many others, though local, are plentiful 

 enough, lyet, from their smaller size, or th^il^ cdncealed 

 stations, they make no materrafl change t^n- the ^{)^earatice of 

 the coast., " It is easy to perceive," sayb'Dn Greville, *^ that 

 some species, Gelidium corneum, Phyllophora rubens, and 

 Sphserococcus <:oronopif()lius, for example, becan*ie more plen- 

 tiful and more luxuriant as we travel from north to south; 

 and, on the other hand, that Ptilota plumosa, Rhod6mela 

 lycopodic)ides, Rhodomenia sobolifera, and several others, 

 occur more frequently, and in a finer state, as we approach 

 thei>nort}>* Qdoothaliia dentto and Rhod^rriia cristata are 

 co^fin^d jto >the northern pai^ts-of Great' Britain'; whil^ the 

 Cystosefifae, JFucuSi tubercul«itus^ Haliseris^polypOdioide^i'Rhb- 

 donjiieijiaJubsLtdirR. Teied^i, MicikiycMdia ' glandulosa, ■Rht)d'6i- 

 mela ^pij^^astrbides^ < lLa;ua:eneiw tenitis^itti^'^t'Msy'U 'reriif6niirs, 

 an4 m^i»y!/(ix1ihetos»,»*rei<K)nfi«hied^'tb^the^feoUthei'tt parts. 'Oih^rs, 

 agaia, ,sufcih. asitlieyj^uci ifi genemli the iaminaVie?ae, itiahy 

 Dele^feri(^,'«omejNito^ylkef Ladr^ntf^, Gasti-fdia, anfd Ghoir- 

 dri,,!poigj&efis 4i0i0i extended « a ratige to be influenced by^any 

 change « of )te!mpearatHire ^between- thfe Ti6ii!herh ■ boiinddry 'of 

 Scotland alnd the soath-w^terni poilit of England. '^ '"(Inti^M.', 

 p. x.) i The causes which influence the distfribution of the 

 ^'Ig^ or^ a (particular coast are not' well known. Temperature 

 is one jf but there are- many faicts <whi^h the admission of this 

 cause will <iK)t explain. " A few yatds is,4n s^onie instances,' 

 sufficient to create a change ; and the space of three or four 

 miles a very striking one ; " not merely in regard to species, 

 but in their luxuriance and rapidity of developement. The 

 nature of the soil, according to Dr. Greville, has here much 

 influence. " Thus," says he, " calcareous rocks favour the 

 production of some species, sandstone and basalt that of 



