HANDBOOK OF SEA-WEEDS. 11 



C. rubrum is the most frequent, and it is found in every latitude, 

 almost from pole to pole. It is very variable in aspect, but can 

 always be recognized by its fruit. C. diaphanum is a very hand- 

 some species, growing often in rock pools along with the other. 

 There are about fifteen native species altogether, some of them 

 rare, and all very beautiful, both as displayed on paper and seen 

 under the microscope. Crouania attenuata is a beautiful plant, 

 parasitic upon a Cladostephus or Corallina officinalis. It is how- 

 ever extremely rare, being only found in England about Land's 



Fig. 5. Species of Callithamnion. 



End. A more common and conspicuous, but equally handsome 

 plant is Ptilota plumosa (Fig. 9), which is mostly confined to our 

 northern coasts ; although P. sericea, a smaller species, or variety, 

 is common in the south, and easily distinguished from its congener, 

 which it otherwise greatly resembles, by its jointed branchlets 

 and pinnules. Callithamnion, Halurus and Griffithsia, articulate 

 like Ceramium, furnish also several handsome species. (Fig. 5.) 

 The group Spyridiaceae contains only one English plant, Spy- 

 ridia filamentosa, which is curiously and irregularly branched, the 

 branches being articulate and of a pinky red. One of its kinds 



