24 INTEODUCTION. rV.' 



occasionally ripened in the ojDen air in Devonshire, and Magnolia grandiflora 

 attaining an arborescent size. The remaining marine vegetation of the Florida 

 Keys, as we shall presently see, has a greater resemblance to that of the 

 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 of the species of Algee of the east coast of North America 

 are identical with those of Europe — a very large portion when we contrast it with 

 the strongly marked difference between the marine animals of the two shores ; the 

 testacea, and to a gi'eat extent even the fishes of the two continents, being 

 dissimilar. The European species, on the same length of coast, are greatly the more 

 numerous, 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 

 Algaa, were the local circumstances favourable to their growth. 



As Alg£e are little indebted for nourishment to the soil on which they grow, 

 merely requiring 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 favourable 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 Fuci, or other social species, 

 which cover the exposed surface with a large number of individuals, to the destruc- 

 tion of more delicate species. The rocks, then, most adapted for Algge are those 

 in which, here and there, occur deep cavities afibrding shelter from the too 

 boisterous waves. In these, on the recess of the tide, a tide pool or rock basin 

 preserves the delicate fronds from the action of the sun. The rare occurrence of 

 such situations on the American coast is doubtless a reason of the comparative 

 poverty of the marine flora. 



This comparative poverty is observable even in the common littoral Fuci or Rock 

 Kelp. In Northern Europe, besides several rarer kinds, six species (namely Fucus 

 serratus, vesicidosics, nodosus, canaliculatus ; Halidrys siliguosa ; and Himanthalia 

 lorea) are extremely common, four of them at least being found on every coast. In 

 America, Fucus vesiculosus and nodosus alone are commonly dispersed ; F. serratus 

 and canalicidatus have not 3''et been detected ; and the Halidrys and Himanthalia 

 rest on very uncertain evidence: so that of the six common European kinds, only 

 two are certainly found in America. This deficiency in FucacecB is, in degree, made 

 up for in Laminainacece, of which family several are peculiar to the American shore, 

 the most remarkable of which is the Agarum or Sea Colander, 



Among the red Algte (or Rhodosperms), species with expanded, leaf-like fronds 

 are proportionably less numerous than on the European side. Delesseria sanguinea 

 is absent on the American shore, where its place is supplied by D. Americana^ a 

 species of equally brilliant colouring, but lower in organization, connecting 

 Delesseria with Nitopiliyllum. This latter genus, of which there are so many fine 

 European species, is scarcely known in North America. A few scraps of Nitophylla 

 (almost too imperfect to describe), picked up at the mouth of the Wilmington 



