P l a t e LIX.
DUMONTIA FILIFORMIS, Grev.
Gen . C h a e . Frond cylindrical, membranaceous, fiUed with watery gelatine,
tu b u la r; its walls composed externally of minute roundish oeUs, internally
of elongated cellules, disposed in filaments. Fructification of
two kinds, on distinct individuals; 1, roundish tetraspores immersed
in the surface cellules; 2, clusters of obovate spores attached to the
inner surface of the membrane of the frond. D x jm o n t i a [Lamour.)
in honour of M.Bumont, a French naturalist.
D u m o n t i a fiUformis; frond undivided, attenuated to each extremity,
pinnated with long, simple, tapering branches.
D um o n t ia fihformis, Grev. Alg. Brit. p. 165. t. xvii. Hook. Br. M. vol. ii.
p. 308. Wyatt, Alg. Banm. no. 31. Harv. in Mack. FI. Hib. part 3. p. 188.
Harv. Man. p. 51. Hook.fil. FI. Ant. p a ili. p. 189. Kiitz. Fhyc. Gen.
p. 394. t. 74. f. 2. Fndl. 3rd Suppl. p. 39.
D um o n t ia in c ra s s a ta , Lam. Ess. p . 4 5 .
H a l y m e n ia fihformis, Ag. Sp. Alg. vol. i. p. 214. Syst. p. 245.
C h o n d e ia p u ip u ra s c e n s , Grev. El. Edin. p . 2 9 0 .
G a s t r id iu m filiforme, Lyngb. Hyd. Ban. p . 6 8 . 1 . 1 7 .
Co n f e r v a fihformis, El. Ban. 1 .1480. f. 2.
U lv a fih fo rm is, Wahl. FI. Lapp. p . 5 0 8 .
Var. (3. crispata; frond broad, compressed, waved, curled and twisted.
D um o n t ia filifonnis /3. crispata, Grev. Alg. Brit. p. 165. Harv. I. c.
H .a lym bn ia pnrpurascens S- crispata, Grev. Crypt, t. 240.
H a b . On rocks and stones in the sea, at half-tide level. Annual. Summer,
in places exposed to tidal currents. Common.
G e o g r . D i s t r . Shores of Europe. Southern Ocean.
D e s c r . Root, a smah disc. Fronds solitary or tufted, from one to twenty inches
in length, and from a tenth of an inch to half an inch in width, cylindrical
or compressed, tubular, with an undivided stem furnished with alternate or
irregularly disposed, lateral, simple branches; both stem and branches
tapering at the base, and much attenuated towards the extremities, more or
less waved, and flexuous. Sometimes the main stem is short, and comparatively
slender; the branches being much longer, and of greater diameter :
sometimes the branches are short, and the stem long. In almost all cases
the tube is unequally distended or w'avy, a peculiarity which in var. ;3, is
very much exaggerated. In this the frond is much twisted, often in a strong
spii'al, and the membrane excessively curled and puckered. Fructification;
1, tetraspores (wliich I have not seen); and clusters of obovate spores
attached to the inner siu-face of the tube, abundantly produced in summer.
Substance membranaceous, gelatinous within, adhering to paper in drying.