two thorn-like processes near the apex. In other varieties the decomponnd-
pinnate character is less obvious; there is less distinction into a primary
stem and branches, and all parts of the frond are more erect, sometimes
being very erect. In other specimens the lateral pinnae are short and nearly
simple : and in a singular variety (possibly a species) found by Mrs.
Griffiths, at Larderham, Torbay, every division of the plant is patent and
divaricate, and the substance stiff and rigid. Late in the season the finer
upper ramuli disappear ; the frond becomes unsightly and distorted, and
rough with the stumps of its broken ramuli. In this state it survives through
the winter, and next spring produces a new and copious crop of branches.
Ceramidia nearly sessUe, broadly ovate. Tetraspores immersed in the tips
of distorted ramuli. Siphons about twenty, narrow, surrounding a large
cavity. Colour purple in the finer branches, very dark, and brownish below,
rarely brown-red ; darkening and almost blackening in drying. Substance
in the stem rigid ; in the ramuli soft, flaccid, and adhering, hut not strongly,
to paper.
This species varies considerably in appearance according to the
time of year at which the specimens are collected, the autumnal
or winter individuals being coarse and bushy, with crowded
ramuli, while those gathered in spring and summer are of the
feathery character represented in our figure. Some are of a dark
purple, and others are of a dull b row , or pale; but all become
much darker and even black in drying. From all the British
species of the section to which it belongs, P. nigrescens may be
known by the distantly pinnated ramuli, the very large number
of siphons, and the comparatively wide central tube. When
bearing antheridia the tips of the branches are yellow.
I am unable to distinguish P. atropurpúrea from a common
form of the species. | | !
T 1
'iih
Fig. 1. P o l y s i p h o n i a n i g r e s c e n s :— the natural size. 2. A small branch.
3. Apex of a ramulus with ceramidium. 4. Ramulus with tetraspores.
5. Antheridia. 6. Articulations of the stem. 7. Transverse section of
the stem;— all mag.