CEEAMIACE^. 205 



the same plant, sornetimes on the same branch, as the 

 tetraspores. They do not, moreover, contain spores of 

 the usual form, but only a very fine powder. 



Ceramium tenuissimum. The slender Cerammm. 



Pronds tufted, two to five or six inches long, of the thick- 

 ness of hair throughout, much and forkedly branched, with 

 very wide axils ; branches and branchlets spreading ; tips 

 slightly curled inwards ; nodes swollen, coated with coloured 

 cellules ; internodes transparent, those of the middle of the 

 stem from four to six times as long as broad, becoming 

 shorter above. Spore-clusters surrounded by involucral 

 branchlets, near the tips of short branches ; tetraspores 

 prominent, on the outer side of the nodes of short branches, 

 one or more on each node. 



There is a very close resemblance between this species 

 and Cerammm strictum, but at the same time both pos- 

 sess suflBcient distinctive characters to be identified with 

 certainty. C. tenuissimum has its tetraspores arranged 

 on the outer side only of the branchlets, one or two on 

 each node, and the axils of the divisions of its fronds 

 are very wide-spread. In C. strictum, on the other hand, 

 the tetraspores extend all round the nodes, several in 

 each, and the axils of the branches are comparatively 

 acute. 



Ceramium gracillimum. The very slender 

 Ceramium. 



Frond two or three inches long, excessively slender 

 throughout, gelatinous and tender, irregularly divided in 

 a forked or alternate manner ; branches set with minute, 

 forked, fan-shaped branchlets ; tips incurved ; nodes awol- 



