294- BRITISH SEA- WEEDS. {Tlltodospermea;. 



Griffiths, Torquay ; Capt. Carmicliacl, Appin ; by Professor 

 Harvey (who kindly sent inc specimens) in Ireland; found 

 also on the Irish shores by Mr. Templeton and by Mr. 

 M'Calla ; by the latter abundantly at Eoundstonc. 



It has a very thorny habit, as the specific name implies. 

 To the naked eye it bears some resemblance to young speci- 

 mens of JRyiijoJdcea fruticulosa, but it is distinctly jointed 

 and more flaccid. See a good figure of it in Phyc. Brit., 



PI. CCXXXVII. 



3. POLYSIPHONIA ATRO-RUBESCENS, GreVllh. 



Hab. On stones and rocks in the sea, near low-water 

 mark. Annual. Summer and autumn. Not uncommon. 



It has borne a good many difi'erent names, — Conferva 

 nigra, Ihitdiinsia demidata, Folysijihonia hadia, P. Agardh- 

 iana, and finally P. atro-ruhescens : the specific name was 

 given by Dillwyn. It is got on the coast of Ayrshire. One 

 of the best distinguishing marks, though not constant, is 

 the spiral curving of the tubes. Colour, a dark red, be- 

 coming brownish ; the substance is somewhat rigid, so that 

 it does not always adhere to paper. See in ' Phycologia 

 Britannica,' PI. clxxii., a very good figure, natural size, 

 and portions of the stem and fruit magnified. 



4. PoLYsiPiiONiA spiNULOSA, GrevUle, 



