The general aspect is that of a tree. The branches, in well-grown speci- 

 mens, are 3-6 inches long, ovate in outline, and several times decompounded, 

 the lesser divisions springing very irregularly, and the main rachides being- 

 more or less zigzag. All the angles are acute, and the branches and 

 ramuli more erect than patent. The smaller ramuli are evidently con- 

 stricted at their insertion, and taper to an acute point. The conceptacles 

 occur sparingly in the ramuli, one in each fertile ramulus, towards its 

 centre ; they are globose, and of nearly twice the diameter of the part where 

 they occur. The tetraspores are more common, and are dispersed through 

 the smaller divisions of fronds that produce them. The number of axial 

 filaments in the tube varies with the age of the specimen ; being few and 

 distant in young parts, and densely crowded in old ; the larger peripheric 

 cells are generally in a double row. The colour when growing is a deep 

 full red, which becomes a brilliant crimson (retained in drying) if the plant 

 be steeped in fresh-water. The substance is cartilaginous and rather soft ; 

 and the plant generally adheres closely to paper in drying. 



The genus Bhabdonia is in many respects closely allied both 

 to Arescltougia and Erythroclonium, but differs in the want of a 

 principal axial filament. It agrees in structure and habit with 

 Solieria, but differs essentially in the structure of its concep- 

 tacles. 



The species here figured is that on which the genus was origi- 

 nally founded, to which others, Australian and American, have 

 since been added. Having had full opportunity in Australia 

 and Tasmania of studying R. coccinea and B. nigrescens in a 

 fresh state, I cannot agree with my friend Sonder in uniting 

 them. One invariably becomes brilliant, and the other becomes 

 darker in fresh-water, and in drying, and the habit and sub- 

 stance are also somewhat different. 



Fig. 1. Rhabdonia coccinea, — the natural size. 2. A ramulus with an im- 

 bedded conceptacle. 3. Cross section of the frond. 4. A tetraspore. 5. 

 Cross section of a conceptacle. 6. One of the spore-threads removed : — 

 the latter figures variously magnified. 



