Ser. RhodospeumkjE. Earn. L 



atcrenaacea. 



Plate XV. 



LAURENCIA GREVILLEANA, Harv. 



Gen. Char. Frond cylindrical or piano-compressed, linear, pinnately- 

 branched, cartilaginous, the apices obtuse, composed of two strata 

 of cells ; the inner of oblong, angular cells, shorter toward the cir- 

 cumference; the outer of small, roundish-angular cellules. Fruit: 



1, ovate, sessile ceramidia, containing a tuft of pear-shaped spores ; 



2, tripartite tetraspores, imbedded, without order, beneath the tips of 

 the ramuli. — Laurencia (I/amour.), in honour of M. De laLaurencie, 

 a French naturalist. 



Frons teretiuscula v. plano-compressa, linearis, pinnato-ramosa, cartilaginea, api- 

 cibus obtusis, ex stratis duobus contexta ; strato medullars ex cellidis oblongis 

 extus sensim brevioribus, corticali ex cellulis minoribus rotundo-angulatis co- 

 loratis. Fruct. : 1, ceramidia ovata, sessilia, intra pericarpium crassiusculum 

 fascicidnm sporarum pyriformium fovenlia ; 2, tetraspores triangule divisce, 

 infra apicem ramulorum sine ordine immence. 



Laurencia Grevilleana ; deep rosy-crimson ; frond flat, exactly distichous, 

 decompound-pinnate; pinnae alternate, erecto-patent, on a straight 

 rachis ; pinnules oblong, inciso-crenate or pinnatifid, the lowest ones 

 minute, gland-like; fruit? 



L. Grevilleana ; purpureo-coccinea ; fronde complanata eximie disticha decompo- 

 sito-pinnata ; pinnis in rackide stricta alternis erecto-patenlibus ; pinnidis 

 oblongis inciso-crenatis v. pinnatijidis, inferioribus minutis glandidceformibus ; 

 fructiferis ? 



Laurencia Grevilleana, Harv. in Trans. R. I. Acad. v. 22. p. 545. Harv. 

 Alg. Austr. Exsic. n. 227. 



Hab. On the under surface of ledges of the coral-limestone reefs at 

 Eottnest Island, Western Australia, at extreme low-water mark, 

 W. H. H. 



Geogr. Distr. As above. 



Descr. Root a spreading, lobed disc. Fronds tufted, 6-8 inches long, 2-3 

 lines in diameter ; the lower part of the principal stem thickened in the 

 middle, the upper part and all the branches and their divisions quite flat, 

 thickish. The ramification is perfectly distichous, of a pinnate character, 

 and full-grown specimens are about thrice pinnated, the ultimate pinnules 

 being either denticulate or more or less pinnatifid. The main rachis is 

 usually quite simple, but sometimes is once or twice forked ; the pinnae and 

 their subdivisions are alternate, and issue at an angle of 30° to 45°. All 

 the sinuses or axils of the ramifications arc obtuse. Some specimens occur 



