which it bears only an outward resemblance, differing very essentially
in microscopic characters. In the original F . spinulosa there
are but four siphons surrounding the central cavity; here there
are twelve. By comparing the figure now given, with that of
P. mbulifera, it will be seen that there is a much nearer relationship
to that species than to any other British one, and except
for some differences of habit, and minor differences in structure,
the two might perhaps be brought together. Prof. J. Agardh,
however, who saw specimens of om- P. simulans during his visit
to England, pronounced them distinct, an opinion also entertained
by Mrs. Griffiths, and in which, though not without
misgivings, I concur. As it is no longer possible to retain the
name spinulosa for the plant here figured, I propose that of
simulans, alluding to its deceptive charac terfor it looks sometimes
like P . mibulifera, sometimes like P . nigrescens, and has
been mistaken, as we have seen, for P . spinulosa.
It is one of our rarer species, although found in several
distant locahties.
Fi«-. 1. P o l y s i p h o n i a s im u l a n s :— the natural size. 2. A small branch.
° 3. Ceramidium. 4. Ramulus with imbedded tetraspores. 5. Joints from
the stem, and young ramulus with apical fibres. 6. Transverse section of
the stem;— a llí
ill I