36
THE
'
-
'
become adapted to these conditions ; if'the shore is rocky
_
'
and there” are pools in this region they'are lled with the
"
green weed, Enteromorpha, consisting of long 'tùbular
fronds.
In the summer the pools are ”apt to dry up, the
weed is killed and only 3, line of white marks this Enteromorpha belt.
About the region of high—water mark there
is a belt, in breadth from a few feet to-about ve yards
varying according to the slope of the shore, of the yellow or
olive coloured “ Channelled wrack ”
(Pelvetia canaliculata),
distinguished from the other brown weeds by its narrower
fronds.
(Plate 9.)
From the base of this belt to low—
water mark the rocky shore is covered with a tangle of
brown weeds known generally as_the fucoid zone, because
most of the weeds are members of the genus Fucus.
The“
various kinds of Fucus are arranged in quite a denite
'
series.
Next to the Pelvetia comes the ”broad fronded
,
Fucus platyaarybw, followed by a broader belt of Ascoÿhyl—
Zum
%odosum or "‘ Knotted- wrack,” with exceptionally
long trends bearing a single row of bulbous air
'
down the centre;
This weed is easily to be distinguished
'
because on it ‘imÏariably‘ grows a small red weed (Polysi— ,
ÿh0_m‘a‘ ‘fastigiata).- The next belt_ Consists of Fnous
_
vesicul'oSu-s
or
"‘
Bladderlwrack ”
(Plate 9), to be distin—
guished by the pairs of air bladders along the fronds Which,
when -dried, “
pop
”
sharplywhen pressed. Nearest low—
water mark is
the ;coinmonest and most strongly growing
of all these .fucoids, Fucùs
the “ Notched wrack ”
which, as its name tells us, has'toothed serrations along the
of the fronds.
belts of Fucus are not
always present, depending on loCal conditions, the amount
of fresh Water, exposure, etc., While,there are “several less
common species which we haVe not mentioned, but generally
Speaking the above types Will“
found on any typical .
_
rocky Shore.
They-are terrriinated, qùite-sha—rply, at low"—