two thorn-like processes near the apex. In other varieties the decompound- 
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 pinnze 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 sessile, broadly ovate. Zetraspores immersed in the tips 
of distorted ramuli. Stphons about twenty, narrow, surrounding a large 
cavity. Colowr 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, but not strongly, 
to paper. 
POI 
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 sprmg and summer are of the 
feathery character represented in our figure. Some are of a dark 
purple, and others are of a dull brown, or pale; but all become 
much darker and even black in drymg. From all the British 
species of the section to which it belongs, P. xigrescens 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. 
IT am unable to distinguish P. atropurpurea from a common 
form of the species. 
Fig. 1. PotystrpHONTA NIGRESCENS :—the natural size. 2. A small branch. 
8. Apex of a ramulus with ceramidium. 4. Ramulus with tetraspores. 
5. Antheridia. 6. Articulations of the stem. 7. Transverse section of 
the stem :—all magnified. 
