Plate CICYEL.
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P l a t e CXCVIII.
LAURENCIA TENUISSIMA, Grev.
Gen . C h a r . Frond cylindrical or compressed, linear, pinnately branched,
the apices obtuse; structure cellular, sohd. Fructification of two
kinds, on distinct individuals ; 1, ovate capsules (ceramidia), furnished
with a terminal pore, containing a tuft of pear-shaped spores; 2,
triparted tetraspores, imbedded in the ramuli. L a u e en c ia (^Lamour.),
—in honour of M. de la Laurencie, a French naturalist.
L aueenc ia tenuissima; frond filiform, terete, irregularly divided; branches
long and virgate, clothed with very slender, setaceous ramuli, which
taper to the base and apex.
L aueencia tenuissima, Grev. Alg. Brit. p. 113. Eoolc. Br. M. vol. ii. p. 396.
Wyatt, Alg. Banm. no. 33. Harv. Man. p. 70. Harv. in Hook. Bond.
Bourn. Bot. vol. vi. p. 401. Endl. 3rd Suppl. p. 43. J. Ag. Alg. Medit.
p. 113. Harv. in Mack. El. Hib. part 3. p. 198.
Al sid ium tenuissimum, KuU. Phyc. Gm. p. 434. t. 55. f. 1.
Chondeia tenuissima, Ag. Sp. Alg. vol. i. p. 353. Ag. Syst. p. 305. Sp-eng.
Syst. Veg. vol. iv. p. 340.
Gi &aetina tenuissima, Lamour. Ess. p. 48.
F u cus tenuissimus, Good, and Woodw. lAnn. Tram. vol. iii. p. 315. t. 9.
Turn. Syn. p. 35. Turn. Hist. 1 .100. E .Bot. 1 .1883.
H a b . On rooks and stones between tide m arks; generally in shallow pools,
about half-tide level. Annual. Summer. Very rare. Weymouth,
Goodenoiigh and Woodward. Isle of Wight, Rev. 6 . R , Leathes.
Torbay, Mrs. Griffiths. Bovisand, Rev. W. S. Hore. Ballycotton,
Co. Cork, Miss B a ll. Jersey, Miss White and Miss Turner.
Geogr. d is t r . Atlantic coasts of France and Spain. Mediten-anean and Black
Seas. East coast of North America. Tasmania.
D e sc e . Root accompanied by interwoven fibres. Eronds densely tufted, from
six to eight or ten inches long, half a line in diameter below, attenuated
upwards. Stem either simple or divided into four or five principal portions,
each of which is furnished with closely-set, slender, alternate, vu-gate,
erecto-patent, undivided branches, which sometimes bear a second set of
similar, but smaller branches; the whole frond, or its principal divisions
having a pyramidal outline. Branches slender, tapering to the base and
apex, more or less densely clothed with setaceous ramuli. Ramuli simple,
two to fom- lines long, straight, or somewhat curved at base, and tapering
to tbe apex, quadrifarious, irregularly inserted, either scattered or rarely
somewhat fascicled. Occasionally, in luxuriant specimens, the ramuli bear
a few of a second order. Capsules ovate, subsessile, borne profusely on the
sides of the ramuli, containing a tuft of pear-shaped spores. Tetraspores
contained in the ramuli, globose, scattered. A transverse section of the
stem shows six cells of large size surrounding the central one, with a wide
border of smaller cells. Substance between cartilaginous and gelatinous.
I