axis or string of large cells, wliicli runs tliroiigli the pinnule as well as
(with some mollification) through every pari of the frond. Enffiification ;
1 , roundish, tripai'tite, external tetraspores seated on minute pedicels, which
fringe the margin of slightly abbreviated pinnules ; 2, on distinct plants,
clustered/are//«, surrounded by an involucre of several subulate ramuh,
and borne on the apex of abbreviated pinnules. Co/om)-a dark, full red,
occasionally with a brownish tinge. Substance cartilaginous, rather rigid,
more or less perfectly adhering to paper in drying.
Our figure and description apply solely to tlie var. a. of Turner,
which, though abundant on the shores of Scotland and the north
and west of Ireland, is rare in England, and quite unknown on
our southern shores. As far as my experience goes it invariably
grows on the stems of Laminaria digitata, which it often clothes
with a rich feathery fringe. The var. /S. of Turner, which is the
common plant of the south of England, as invariably grows
on rocks ; and preserves its characters so constantly that I cannot
help regarding it, with Kiitzing, as a distinct species. In doing
so I am reluctantly compelled to dissent from the opinion of
Mr. Turner, who says, “ that no Fucus whatever exhibits more
regular gradations between the most narrow and delicate, and the
broadest and most cartilaginous individuals ; in consequence of
which no attempt was ever previously made to separate it into
different varieties.” I cannot observe this gradation ; to me the
two forms appear to be easily distinguishable by tbe naked eye
in every case ; and present very distinct microscopic characters.
Besides this, their geographical range and habitat are different ;
for though on our northern shores both are found, yet further
north the var. a. alone is met with ; and further south, as on the
southern shores of England and the shores of Erance and Spain,
the var. /S. is exclusively seen. Add to this, that the first is never
found on rocks, and the last always is ; that the parasites which
commonly infest them are different ; that one is a far stouter and
more cartilaginous plant than the other; that the microscopic
appearance of their pinnules is very dissimilar ; and we shall, I
think, have sufficient specific characters to separate them.
Fig 1. P t il o ta p lum o sa -.— o f the natural size. 2. A pectinated pinnule. 3.
O n e of the ultimate laciniæ. 4. An involucre. 5. Favellæ, removed from
the same. 6. A lacinia bearing tetraspores. 7. One of the tetraspores
more or less highly magnified.
I
A . »hi