CERAMIACE.E. 69 



DELESSERIA'CE^E. In this family, the typical or 

 most highly developed genus of which, Delesseria, has 

 beautiful leaf-like rose-red fronds, we shall examine 

 the common Plocdmium coccin'eum (PL IV. figs. 23 

 and 22) . This is of a fine red colour ; the fronds are 

 from 2 to 12 inches long, and consist of numerous 

 branched and bushy filaments. These are compressed, 

 with the branchlets arranged in alternate rows on the 

 two margins of the stem. The end branchlets are 

 acute and pectinate (pecten, a comb), or arranged 

 like the teeth of a comb. The cells of which the fila- 

 ments consist are small and angular, giving the surface 

 the appearance of being elegantly netted under a high 

 power. The fruit (fig. 22) consists of globular cap- 

 sules, called coccid*ia (KOKKOS, a berry), placed in the 

 axils or forks at which two branches separate, and 

 containing a mass of angular spores. There are also 

 tetraspore-pods (stichidia), as in Dasya ; and tetra- 

 spores (fig. 24) in little leaf-like altered branches 

 (fig. 21), called spor'ophylles (o-Tropa, seed, $>v\\ov, 

 leaf), and antheridia are present. 



RHODYMENIA'CE^E. In this family we have Hyp'nea 

 purpuras 1 cens (PL IV. fig. 35). The filamentous pale 

 purple frond of this sea-weed is from 6 inches to a 

 foot or more in length, the branches being alternate 

 and spreading. The fructification consists of capsules 

 or coccidia (fig. 32), immersed in the branches, and 

 containing the spores (fig. 34). Tetraspores also 

 occur in the cells of the surface of the filaments. 



CERAMIA'CE^;. This is the last family to be noticed. 

 Cerdmium nodosum (PL IV. figs. 10 and 11), which 

 belongs to it, is a most delicate and elegant filament- 

 ous sea-weed, commonly found attached to other sea- 

 weeds. The filaments are hair-like or capillary, irre- 

 gularly dichot'omous ; they consist of colourless cells, 

 3 or 4 times as long as broad, and with thick walls. 

 The junctions of the cells are swollen (fig. 11), and 

 covered with very minute dark red cells, giving them 



