200 BRITISH SEA-WEEDS. 



which appears to be the only locality in this country 

 where it is to be obtained. My friend Mr. Stevens has 

 collected it at Torquay, and Mr. Gatcombe at Plymouth, 

 and I have to thank both these gentlemen for kindly sup- 

 plying me with specimens. This species generally grows 

 parasitically on other sea- weeds, at and beyond low-water 

 mark. It is annual, and fruits in summer. 



Genus XCV. CERAMIUM. 



Prond thread-like, jointed, forked or pinnate, more or less 

 coated with small roundish cells, which are irregularly 

 arranged. Spore-clusters (favellse) enveloped in a trans- 

 parent sac, stalkless, set on the branches and surrounded 

 by a collar of short branchlets ; tetraspores tripartite, 

 roundish, formed from and among the bark-cells, prominent 

 on the surface of the frond. — Cebamitjm, from the Greek 

 keramos, a pitcher. 



A large number of species are included in this genus ; 

 but recent writers on the subject are not agreed as to 

 whether certain forms are entitled to specific rank, or 

 should be considered mere varieties. There are eleven 

 British species which are pretty firmly established, and 

 which represent the principal sections into which the 

 genus is usually divided. These sections are : — 



1. Frond covered throiigliout with, small barh-cells. — This 



contains O. rubrum. 



2. M-ond with nodes covered to a definite limit with harlc- 



cells, the internodes heinff transparent. — This contains 

 C. diaphanum ; G. Deslongchampsii ; C. tenuissimwn ; 

 G. gracillimum ; G. strictv/m ; and C. fastigiatum. 



3. Frond with nodes covered to a definite limit vjith lark- 



cells, and armed with one or more spines, the inter- 



