ñ H / f r C L J T V J I .
Ser. E hodospermeæ. Fam. Rhodomeleoe.
P l a t e CCLXXVII.
POLYSIPHONIA NIGRESCENS, Grev.
G e n . Ch a r . Frond filamentous, partially or generally articulate; joints
longitudinally striate, composed of numerous radiating cells or tubes,
disposed round a central cavity. Fructification twofold, on different
individuals: 1, ovate capsules (ceramidia) furnished with a terminal
pore, and containing a tuft o f pear-shaped spores; 2, tetraspores
imbedded in swollen branches. P o ly s ip h o n i a (Oreo), — from
woXas, many, and (nipav, a tube.
P olysiphonia nigrescens ; fronds robust, rigid, and generaUy rough with
broken branches below, much branched and bushy above; the
branches alternate, repeatedly divided in a pinnate manner ; ramuli
distant, elongated, awl-shaped, alternate, the upper ones sometimes
having a few processes near the tips ; lower articulations short, upper
rather longer than broad ; siphons about twenty, surrounding a large
tube ; ceramidia broadly ovate, sessile or nearly so.
P olysiphonia nigrescens, Harv. in Hook. Br. M. vol. ii. p. 333. Wyatt,
Alg. B anm.'aa.\Z'á. Harv.in Mack. M. Hib. Z . H a r v . Man.
ed. 1. p. 88. ed. 3. p. 89. Endl. Zrd Suppl. p. 45. Kiitz. Phyc. Un. p. 431.
t. 50. iv. Sp. Alg. p. 813.
P olysiphonia fucoides, Qrev. M. Edin. p. 308.
H utch in s ia nigrescens, Lyngb. Hyd. Ban. p. 109. t. 33. Ag. Syst. p. 151.
Ag. Sp. Alg. vol. ii. p. 69.
H utch in s ia fucoides. Hook. M. Scot. part 2. p. 87.
Conferva nigrescens, Huds. M. Ang. p. 603. (? ?) Billw. Conf. no. 155. Eng.
Bot. 1 .1717.
Conferva fucoides, Huds. M. Ang. p. 603. With. vol. iv. p. 141. Billw.
Conf. t. 75. Eng. Bot. 1 .1743.
H a b . On rocks, and stones, and attached to Algæ, &c., between tidemarks.
Perennial ? Summer. Abundant on the British shores.
Geogr. D is t r . Atlantic shores of Europe and America. New Zealand.
D esc r. Root a small, discoid expansion. Eronds many from the same base,
from three to twelve inches long or more, sometimes very slender and almost
capillary, sometimes robust, twice as thick as hog’s bristle, simple below,
very much branched and bushy above. The ramification, like almost every
other character of this variable plant, is subject to many anomalies. In
wbat may be considered the typical form, the stem divides into several
principal branches, and the frond when displayed is broadly flabelliform in
outline. Bach main branch is obovate, and closely pinnated with alternate,
erecto-patent secondary branches of similar outline ; and these latter are
doubly pinnate. The ultimate pinnules are subulate, distantly placed,
regularly alternate, rather erect, and either quite simple or having one or
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