IV. 
CHORDARIACEJE. 
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 ; jig. 2, a portion of the perforated frond, magnified ; 
jig. 3, minute piece of the same, showing the surface-cellules, highly magnified. 
Order V. CHORD ARIACEiE. 
Chord areele, Harv. in Mack. FI. Rib. part 3, p. 183. Harv. Man. Br. Alg. 
Ed. 1, p. 45. Ed. 2, p. 44. J. Ag. Sp. Alg. vol. 1 , p. 45. Chord areere, (excl. 
gen.) J. Ag. Alg. Medit. p. 31. Endl. 3rd, Suppl. p. 23. Ene. Ess. p. 33. Meso- 
GLOiACEiE, Kiitz. Phyc. Gen. p. 329- Sp. Alg. p. 539. Chord aiudee (excl. gen.) 
Lindl. Veg. 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. Spores attached to the filaments, and concealed within the substance of 
the frond. 
Natural Character. Root 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 ( Ralfsia ) 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 Leatliesia , whose frond is either a 
shapeless or lobed roundish mass, or a cluster of such growing together like so 
VOL. hi. art. 4. r 
