IV. 
FUCACEiE. 
53 
The Fucacece are rarely deep-water plants. One species (F. canaliculatus ), com- 
mon in Europe, begins to grow at the extremity of high water mark, in places 
where it is exposed to the atmosphere during the greater part of the twenty-four 
hours, and only submerged by the highest tide waves. In such places, though its 
growth is dwarfish, it frequently produces fruit. As it descends in depth toward 
mid-tide level, the frond becomes larger and more luxuriant, and in the space 
between this limit and that of quarter-tide, the greater number of individual 
plants occur. Few straggle into deeper water. This species, of all others, is best 
fitted to resist drought, its fronds being peculiarly dense and leathery ; and in a 
warm day it frequently becomes crisp and dry, and to all appearance baked to 
death, during the recess of the water ; and yet, on the return of the tide, the 
withered fronds expand and become flexible and juicy. Perhaps the non-occur- 
rence of this plant on the American coasts may be owing to the fiercer heats which 
it would be subjected to, in the exposed places that it would naturally occupy. 
With the slight exception of this semi-aerial species, all the ordinary Fucacete 
are characteristic of the space strictly defined by the tide marks, extending 
through the whole range of exposed rock ; over which in temperate latitudes they 
usually spread so densely, that the colour of the sea-shore is as clearly character- 
ised by them, as is the colour of the ground by the species of grasses which con- 
stitute its green mantle. 
A few of the most highly developed genera ( Cystoseira, Sargassum , <Sfc.) are pro- 
ductions of deeper water, commencing to grow at depths at which the Fuel cease, 
and extending into a zone of depth where they are constantly submerged. I am 
not aware that any species has been traced into a deeper zone than that occupied 
by Laminarias. 
One remarkable species of the genus Sargassum has long been famous by the 
name of Gulf weed or Sargazo (sea-lentils), under which most voyagers since the 
days of Columbus have spoken of it. That great discoverer was the first to 
encounter it in modern times, (16th September, 1492) and with his account we are 
therefore most familiar ; but possibly the weedy sea which Aristotle speaks of as 
having been met with by the Phoenicians, at the termination of their voyage, may 
have been an early discovery of the same bank. It is curious that the great bank 
which extends between the 20th and 45tli parallels of north latitude, and in 
40° W. from Greenwich, appears to occupy the same position at the present day as 
it did in the days of Columbus. Between this bank and the American shores, 
various smaller strata and detached masses of seaweed occur, beinar thrown into 
this portion of the ocean by the eddy caused by the sub-circular motion of the 
great oceanic currents. The whole of this immense space of ocean, which is re- 
ported to be thickly covered with seaweed, is computed by Humboldt at upwards 
of 260,000 square miles, an area almost six times as large as Germany ;* but it is 
not to be supposed that all this space is equally clothed with floating verdure. In 
many places the weed occurs in distant and narrow ridges, leaving spaces of clear 
water between. This portion of the Atlantic seems to be the chief settlement of the 
Jolmst. Pliys. Atlas. Atlantic , p. 5. 
