THE MARINE BOTANIST. 101 



and Eytiphlsea, they are internal, and almost en- 

 tirely hidden by a coating* of cells of greater or less 

 thickness. One of the most easily-recognized sea- 

 weeds of the Rhodomela tribe, is the Toothed 

 Odonthalia, our only representative of the leafy- 

 fronded Rhodomelacese. In warmer seas many 

 beautiful species are found belonging to the different 

 genera included under this section. In Amansia the 

 cells of the delicate leaf-like fronds are all regularly 

 twelve-sided, and of exactly the same length ; this 

 structure is what is meant by areolated^ and 

 resembles mosaic work. Of the filiform kinds, 

 Polysiphonia fastigiata is an abundant species, 

 gTOwing in thick tufts of a dark-brown colour, 

 upon the Fucus nodosus. The Polysiphonia are 

 a difficult genus for the learner ; for this reason, 

 only a few of the species are described at length in 

 the following pages. The Scarlet Dasya is a very 

 common species often used in ornamental work; 

 it is the only kind of Dasya common on our shores. 

 The other British genera in this tribe include but 

 seven species 5 in habit they resemble some of the 



