IV. CHORDARIACE^. 121 



of those of New Holland. It would be difficult to determine from dried specimens 

 whether the specimens from these various places were identical or not. The living 

 plant has the aspect of a very open sponge, and is so frail that it cannot be raised 

 from the rocks without laceration, and so weak that it cannot support its own 

 weight when lifted from the water. 



Plate IX. A. Fig. 1. Several fronds of Hydroclathrus cancellatus, growing 

 together, the natural size ; fig. 2, a portion of the perforated frond, magnified ; 

 fig. 3, minute piece of the same, showing the surface-cellules, highly magnified. 



Ordee Y. CHORDARIACEiE. 



Choedaeie^, Harv. in Mach. Fl. Hih. part 3, p. 183. Harv. Man. Br. Alg. 

 Ed. 1, p. 45. Ed. 2, p. 44. /. Ag. Sp. Alg. vol. I, p. 45. Chordarie^, (excl. 

 gen.) J. Ag. Alg. Medit. p. 31. Endl. 3rJ, Suppl. p. 23. Due. Ess. p. 33. Meso- 

 GLOiACE^, Kiltz. Phyc. Gen. p. 329. Sp. Alg. p. 539. CHORDAEiDiE {excl. gen.) 

 Lindl. Yeg. Kingd. p. 22. 



Diagnosis. Olive-coloured seaweeds, with a gelatinous or cartilaginous frond 

 composed of vertical and horizontal filaments (or strings of cells) interlaced 

 together. Sjyores attached to the filaments, and concealed within the substance of 

 the frond. 



Natural Character. Eoot rarely more than a disc of attachment ; in the 

 more perfect kinds it forms a point of fixture, at the base of the stem ; in the less 

 perfect, the whole under-surface of an expanded frond adheres to the object 

 on which the plant grows. Frond very variable in form, but in all cases composed 

 of articulated threads or cells strung together in vertical and horizontal series, 

 variously combined among themselves, but easily separable under the microscope, 

 and either accompanied by mucus or lying in a transparent gelatine. The gelatine 

 varies both in quantity and in degree of tenacity. When little developed, it is also 

 more tenacious, and then the fronds are firmly cartilaginous, or somewhat coria- 

 ceous, and highly elastic. But more generally the gelatine is abundant in quantity and 

 very loose in substance, and then the threads composing the frond lie considerably 

 apart one from another, and the common substance becomes soft and gelatinous. 

 The least organised plant of the order (Ralfisia) has a crust-like frond spreading 

 over the surface of rocks, like one of the Lichens, in circular or oblong patches, and 

 bearing on its surface small prominences which eventually contain spores, mixed 

 with paranemata. Next in development is Leathesia, whose frond is either a 

 shapeless or lobed roundish mass, or a cluster of such growing together like so 

 VOL. m. art. 4. E 



