IMInliVM IM \M T. 109 



Mr. Sowerby. By making a transverse Bection, and ap- 

 plying a more powerful glass, this venation is Been to be 

 caused by an internal rib, composed of denser and more 

 elongated cells than the resl of the frond ; and if the in- 

 ternal structure of the frond affords, in the Floride®, the 

 Buresl generic characters, the presence of Buch a rib i 

 to be essentia] to the genus. 8. coronoptfolius is said to 

 be unknown on the eastern coast of England, and in 

 land it is extremely rare. 



LVIT. GUtACILAEIA. 



185. multipartita [The mcuny-divided Gracilaria) \ frond flat, 

 tender, Bemi-transparent, brittle, dull purplish-red, deeply 

 clefl in an irregularly dichotomous or palmate manner j 

 branches linear-wedge-shaped; apices acute; tubercles coni- 

 cal, very prominent, scattered over the segments, Harv.Phy, 

 Brit Byn.p. 25. (Atlas, PI. XL11I. §ig. L96.) 



Gracilaria polycarpa, J. Ag. Plocaria polycarpa, Endl. Rho- 

 dymenia polycarpa, Grev. Sphssrococcus polycarpus, Qrev, 



Hob. South coasts of England. On rocks and -tones in the 

 sea, in deep water. Perennial? August and September. 

 Very rare. 



However diverse the habit of this species be from that 

 of most other Gracilarice, the structure both of the frond 

 and fruit, as Long since remarked by Mrs. Griffiths, ac- 

 cords much better with the structure than with that of the 

 Rhodymenice. The thick walls of the tubercles, composed 

 of filaments, and the Large internal cells of the frond, are 

 characters not to be overlooked. 



186, compress* {The compressed Gracilaria) ; frond Bucculent, 

 brittle, somewhat compressed, alternately or Bubdichoto- 

 mously branched ; branches long and mostly simple, taper- 

 ing to a fine point ; tubercles ovate or subglobose, Bessile, 



scattered plentifully over the branches; tetraspores tripar- 

 tite or cruciate, Grev, Alg. Brit. p. 125. (Atlas, PI. XML 

 Fig. 11)3.) 

 Plocaria compressa, Endl. GKgartina compressa, Hook. Sphav 



rococcus compressuSj Aa, S. Lichenoides, Grev. 

 Hob* South of England. Cast on Bhore from deep water, at- 

 tached to corallines, etc. Annual. Bummer. Very rare. 

 i, baa something the aspect of <•■ 



voides, but may always be known by its more succulent 

 frond and very different substance. It is as soft and 

 brittle as (>. co^nfervoides is hard and tenacious. It also 



