52 COMMON SEAWEEDS. 



like rows on branclilets. Four siphons are in the 

 stem, and the skin is full of irregular violet cells, 

 which partially conceal them. This is a distinguishing 

 mark : also observe the tufts of thread-like fibres at 

 the end of the branches. 



It grows in all mid-tide and low-tide pools. 



Polysiphonla Ueceolata (the Hair-like Polysi- 

 phonia). — On the stems of Laminaria Digitata, large 

 tufts of this seaweed may be found, varying in length 

 from three to nine inches ; colour, a dark red. Here 

 the pretty seed vessels, instead of being at the tips, are 

 seated on branches, singly — lovety little urns of trans- 

 parent rose-coloured cells, in which we see oblong 

 bodies of deeper hues; and by a little gentle pressure 

 the urns will open their mouths, and the spore-cases 

 come out ; or, if the fruit be tetraspores, we shall 

 find it in single rows at the tips of the ramuli or short 

 branches. Again, we observe only two siphons visible 

 in the stem, for it contains but four, whereas in other 

 species there may be as many as twenty. Of course 

 all this is only seen with a microscope, but one of very 

 moderate power will exhibit these beauties ; whereas 

 simply dried on paper, this Polysiplwnia is black, and 

 hardly to be distinguished from Pohjsiplwnia Fasti- 

 giata. 



PoxsiPHoyiA !N"igeescens. — This is found in mid- 

 tide pools, on rocks or the larger Algce, and is very 

 abundant everywhere in summer. Spread out upon 

 paper, it is long and bushy, quite black, the stems 

 rather bare towards the base. Under the microscope 



