CERAMIACE^. 157 



of different ages. In the young plants the branches and 

 stem will be found to be nearly destitute of these secondary 

 fibres, while old specimens are rendered almost opake by the 

 large number of them. In Callithami^ion the coating cells 

 appear to be introduced into the walls of the original fila- 

 ment, but in more coiupound forms, as in Mlcrocladia and 

 Ptilota, the coating of the primary or axial filament is formed 

 by the addition of one or more strata of small, mostly poly- 

 gonal cells. Such fronds then appear to be inarticulate or 

 cellular, all traces of joints being concealed by the incum- 

 bent cells. The tissue of which the Ceramiacece are com- 

 posed is tender and delicate, and the frond usually adheres 

 strongly to paper in drying, and soon decomposes if left in 

 fresh water. Decomposition instantly shows itself by the 

 colour changing from the clear, pinky red natural to the order 

 to a bright orange ; and this change of colour is accompa- 

 nied by a disagreeable odour and the sudden breaking up of 

 the branches into their component cells. In Griffithsia the 

 disruption of the membrane is accompanied by a crackling 

 noise, convulsive shrinkings, and the sudden discharge of all 

 the colouring matter. This matter, in many of the genus, 

 stains paper in a durable manner with a brilliant crimson, 

 and might doubtless be applied as a pigment. 



There is considerable uniformity in the fructification of the 

 plants of this order. The conceptacular fruit, which is cal- 

 led a favella, is a metamorphosis of a secondary branch. 

 In some it is formed with great regularity, while in others 

 it has a diseased appearance. In CalUthamnioii the favella; 

 are naked, berry-like masses, terminating truncated branches, 

 and are formed by the sudden stoppage of the branch, and 

 the conversion of its apex into a mass of spores. These 

 spores are at first attached to filaments within the favella, 

 but eventually become free. In Griffithsia, Ceramium, and 

 most other genera, the favellye are protected by a whorl of 

 short ramuli standing round them like the involucre to a 

 flower. In Ceramium the favellae are sessile, and either naked 

 or (more commonly) involucrate. The tetraspores are rarely 

 aggregated, being usually scattered along the lesser branches 

 and ramuli. In Callithamnioii and GriJJithsia they are ex- 

 ternal, attached by a point at the base to the ramulus on which 

 they sit ; in Seirospora they are formed at the expense of the 

 cells of the ramulus, each cell becoming transformed into a 

 tetraspore ; and in Ceramium and Ptilota they are either 

 wholly immersed among the peripheric cells, from some of 



