158 BRITISH SEA-WEEDS. 



This species grows on rocks and shells near low-tide 

 mark, and occasionally, when the rocks are formed of 

 granite, in shallow shore-pools. It appears to prefer 

 situations where it is exposed to the air when the tide 

 goes out and where it is washed and beaten by the waves. 

 It is common on the western coasts of Scotland and 

 Ireland, and occurs less frequently in several English 

 localities, chiefly on the south coast. This is the only 

 plant of the Order Helminthocladice on which tetraspores 

 have been found. 



Genus LXV. HELMINTHOCLADIA. 



Frond cylindrical, elastic, composed of filaments, set in 

 gelatine ; those of the axis simple, longitudinal, loosely in- 

 terwoven into a cord-like column, surrounded by other 

 oblique, communicating filaments, from which issue the 

 horizontal necklace-like, forked filaments, which compose the 

 periphery. Fructification, masses of spores seated among 

 the filaments of the periphery ; tetraspores unknown. — 

 Helminthocladia, from the Greek elmins, a worm, and 

 klados, a branch. 



Helminthocladia purpurea. The purple Helmin- 

 thocladia. 



Fronds from eight inches to two feet or more in length, 

 tapering from the centre towards either end ; stem mostly 

 undivided ; branches opposite or alternate, irregular, numer- 

 ous ; branchlets slender, undivided ; colour varying from a 

 deep purple-red to a dull pink, rapidly given out in fresh 

 water, and becoming brown in drying. Root a small disc. 

 Fructification, globular masses of spores among the threads 

 of the periphery. 



In the ' Phycologia Britannica ' this plant is figured 



