208 BRITISH SEA-WEEDS. 



touch, very slender, of nearly equal diameter throughout, 

 repeatedly forked ; axils spreading, the branches frequently 

 furnished with forked branchlets ; tips strongly hooked in- 

 wards ; nodes coated with a broad band of small, coloured 

 cellules, and armed with irregularly-inserted, slender, colour- 

 less, one-jointed spines ; internodes transparent, those of 

 the lower part of the frond twice or three times longer than 

 broad, those of the upper much shorter. Spore-clusters 

 generally near the tips of the frond, or of the side branches, 

 often axillary, surrounded by strongly incurved branchlets ; 

 tetraspores prominent on the outer edge of short branchlets, 

 one or two in each node. 



This is a common species, and very easily recognized 

 under the microscope by the form and arrangement of 

 the spines, which are always present on the nodes of the 

 frond. It grows parasitically on small algse, either in 

 rock-pools or among pebbles, near high-water mark. 

 It is annual, and in perfection in summer and autumn. 



Ceramium acanthonotum. The one-spined 

 Ceramium. 



Fronds growing in dense, intricate tufts, slender, and of 

 equal diameter throughout, repeatedly forked, fastigiate ; the 

 tips of the frond very strongly incurved ; axils spreading ; 

 nodes coated with a broad band of minute, coloured cellules, 

 armed on the outer edge with a single, robust, awl-shaped, 

 coloured, three-jointed spine; internodes colourless, those 

 in the lower part of the frond several times longer than 

 broad, becoming very short at the upper part. Spore- 

 clusters globose, on the sides of the branches, clasped by 

 a single strongly-incurved, armed branchlet ; tetraspores 

 whorled round the nodes, very large and prominent, with 

 a broad, transparent border. 



