THE SMITHSONIAN INSTITUTION. Ill 



It is difFcrcnt witli Padina Pavonia, itself a tropical form, and be- 

 longing to a group peculiarly lovers of the sun. We are not sur- 

 prised that in America this plant should not grow further north than 

 the Keys of Florida, although, under some peculiarly favorable cir- 

 cumstances, it attains a limit 27° further north, on the south coast of 

 England ; for in the land-vegetation of the two coasts there is some- 

 thing like an approach to similar circumstances, oranges and citrons 

 being occasionally ripened in the open air in Devonshire, and 3Ia(j- 

 nolia grandiJJora attaining an arborescent size. The remaining marine 

 vegetation of tlio Florida Keys, as we shall presently sec, lias a greater 

 resemblance to that of tlie Mediterranean than to that of the British 

 coasts ; and this is more in accordance with the land floras^ in which 

 palm trees are a feature in both countries. 



Probably one-half the species of Algae of the east coast of North 

 America are identical with those of Europe — a very largo portion 

 when we contrast it with .the strongly marked difference between the 

 marine animals of the two shores ; the testacea, and to a great extent 

 even the fishes of the two continents, being dissimilar. The Euro- 

 pean species, on the same length of coast, arc greatly the more nu- 

 merous, which appears to be owing to the prevalence of sands, nearly 

 destitute of Alga3, along so great a length of the American shore, 

 and particularly along that portion which, from its latitude, ought to 

 produce the greatest variety of Alga^, were the local circumstances 

 favorable to their growth. 



As Algfo are little indebted for nourishment to the soil on which 

 they grow, merely rec[uiring a secure resting place and a sheltered 

 situation, their number generally bears a proportion to the amount of 

 indented rocks that border the coast. Stratified rocks are more favorable 

 to their growth than loose boulders or stones ; but if the upper surface 

 be smooth without cavities, it is either swept by the waves too rapidly 

 to allow the growth of a vigorous vegetation ; or, in quiet places, it 

 becomes uniformly clothed with some of the Fuoi, or other social spe- 

 cies, wliich cover the exposed surface with a large number of individ- 

 uals, to the destruction of more delicate species. The rocks, then, 

 most adapted for Algee are those in which, here and there, occur deep 

 cavities affording shelter from the too boisterous waves. In these, on 

 the recess of the tide, a tid& ijool or rock basin preserves the delicate 

 fronds from the action of the sun. The rare occurrence of such situ- 

 ations on the American coast is doubtless a reason of the comparative 

 poverty of the marine flora. 



This comparative poverty is observable even in tlie common littoral 

 Fuci or Rock Kelp. In Northern Europe, besides several rarer kinds, 

 six species (namely Fucus serratus, vesiculosus, nodosns, cajialicidatus : 

 Halidrys siliquosa ; and Eimanilialia lorea) are extremely common, 

 four of them at least being found on every coast. In America, Fiicuf; 

 vesiculosus and nodosus alone are commonly dispersed ; F. serratus and 

 canaliculatus have not yet been detected ; and the Halidrys and Hi- 

 manthalia rest on very uncertain evidence: so that of the sfa; com- 

 mon European kinds, only tiuo are certainly found in America. This 

 deficiency in Fucacece is, in degree, made up for in Laminar iacece. of 



