A WORLD IN THE WATER 103 



growing on some of the large brown seaweeds, 

 are D. alata and D. sinuosa. Closely allied to 

 these plants are the Nitophyllums, although, as 

 a rule, the species are larger than the average 

 Delesseria. In some cases the leaves of the 

 Nitophyllums are divided into lobes. One of 

 the red seaweeds which is to be found chiefly 

 on our northern shores is the Odenthalia dentata, 

 a plant which is not altogether unlike the 

 brown Fiicus, except in so far as its colour is 

 concerned. 



Of the more delicate kinds of red seaweeds 

 there are a large number, many of which are 

 exceedingly common. In the very large genus 

 of Polysiphonia the stems are often somewhat 

 substantial ; but the ramifications of the 

 branches are frequently of a most delicate 

 description. In the species known as P. 

 elongata the stems are long and thick, but the 

 growth divides itself into thread-hke branches. 

 Many of the smaller kinds grow on the larger 

 seaweeds. Most beautiful of all the red sea- 

 weeds are the Callithamniums. These are of a 

 bright pink colour, and the feathery branches 

 are often almost transparent. The species 

 known as Callithamnium plumula is a small 



