Ser. RHODOSPERME®. Fam. Chondriee. 
Prare CXCVIII. 
LAURENCIA TENUISSIMA, Grev. 
Gey. Cuan. Frond cylindrical or compressed, linear, pinnately branched, 
the apices obtuse; structure cellular, solid.  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 ¢efraspores, imbedded in the ramuli. Lavrencta (Lamour.), 
—in honour of M. de la Laurencie, a French naturalist. 
Lavrencta fenvissima ; frond filiform, terete, irregularly divided ; branches 
long and virgate, clothed with very slender, setaceous ramuli, which 
taper to the base and apex. 
LAURENCIA tenuissima, Grev. Aly. Brit. p. 113. Hook. Br. Fl. vol. ii. p. 296. 
Wyatt, Alg. Danm. no. 22. Harv. Man. p. 70. Harv. in Hook. Lond. 
Journ. Bot. vol. vi. p. 401. Endl. 3rd Suppl. p. 43. J. Ag. Alg. Medit. 
p- 113. Harv. in Mack. Fl. Hib. part 3. p. 198. 
ALSIDIUM tenuissimum, Kiitz. Phyc. Gen. p. 434. t. 55. f. 1. 
Cuonpria tenuissima, 4g. Sp. Alg. vol. i. p. 352. dg. Syst. p. 205. Spreng. 
Syst. Veg. vol. iv. p. 340. 
GiGaRTINA tenuissima, Lamour. Ess. p. 48. 
Fucus tenuissimus, Good. and Woodw. Linn. Trans. vol. iii. p. 215. t. 9. 
Turn. Syn. p. 35. Turn. Hist. t. 100. H. Bot. t. 1882. 
Has. On rocks and stones between tide marks ; generally in shallow pools, 
about half-tide level. Annual. Summer. Very rare. Weymouth, 
Goodenough and Woodward. Isle of Wight, Rev. G. R. Leathes. 
Torbay, Vrs. Griffiths. Bovisand, Rev. W. S. Hore. Ballycotton, 
Co. Cork, Miss Bail. Jersey, Miss White and Miss Turner. 
Geogr. Distr. Atlantic coasts of France and Spain. Mediterranean and Black 
Seas. East coast of North America. ‘Tasmania. 
Descr. Root accompanied by interwoven fibres. Fronds 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, virgate, 
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 four lines long, straight, or somewhat curved at base, and tapering 
to the 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. Sudstance between cartilaginous and gelatinous, 
