24 
INTRODUCTION. 
IV. 
occasionally ripened in the open 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 Algaa 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 great 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 Algae, 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 
Algse, Avere the local circumstances favourable to their growth. 
As Algse 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 groAvth than loose boulders or 
stones ; but if the upper surface be smooth Avithout cavities, it is either SAvept by 
the Avaves too rapidly to alloAv the growth of a vigorous vegetation ; or, in quiet 
places, it becomes uniformly clothed Avith some of the Fuci, or other social species, 
Avliich cover the exposed surface with a large number of individuals, to the destruc- 
tion of more delicate species. The rocks, then, most adapted for Alga; are those 
in which, here and there, occur deep cavities affording shelter from the too 
boisterous Avaves. 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 , vesicidosus, 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 canaliculatus have not yet been detected ; and the Halidrys and Himanthalia 
rest on very uncertain evidence: so that of thesis common European kinds, only 
two are certainly found in America. This deficiency in Fucacece is, in degree, made 
up for in Laminariacece , of which family several are peculiar to the American shore, 
the most remarkable of which is the Agarum or Sea Colander. 
Among the red Algse (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 I). Americana , a 
species of equally brilliant colouring, but loAver in organization, connecting 
Delesseria Avitli Nitophyllum. This latter genus, of which there are so many fine 
European species, is scarcely known in North America. A feAV scraps of Nitophylla 
(almost too imperfect to describe), picked up at the mouth of the Wilmington 
