r 



514 VESICULARIID.E. 



Northumberland, a single specimen (Alder) : St. An- 

 drews, on rocks near low-water mark (Prof. John Reid) : 

 Leith shore (D. Landsb., jim.) : Wick, rare (C. W. P.) : 

 Shetland (Barlee, fide Alder) : Ireland, north, east, and 

 west coasts; very fine near Dublin (W. T.). 



Geographical Distribution. Ostend (Van Ben.) : 

 RoscofF, abundant (Joliet) : Mediterranean (Pallas) : Italy 

 ( Kirch enpauer) . 



V. spinosa grows in tall and graceful shoots, tapering 

 towards the top, and thickly clothed with dichotomously 

 divided and somewhat flabellate branchlets. These are 

 arranged in pairs at each flexure ; and the pairs arise alter- 

 nately from opposite aspects of the stem, so as to give a 

 full and rounded and almost subverticillate appearance to 

 the whole. From the main stems branches are frequently 

 given oW, which are copies of the original shoot ; in large 

 specimens the ramification is luxuriant. The spinous 

 terminations of the branchlets, to which the species owes 

 its name, are not met with on those portions of the 

 zoarium where growth is proceeding : here the tips are 

 rounded and blunt, and the characteristic habit of the 

 species is wanting (Plate LXXIII. fig. 5). 



The tubular fibres, which loosely invest the stems for a 



considerable portion of their length, take their origin on 



the internodes a little above each bend, and tend down- 



; wards, becoming free at the base of the shoot, where they 



act as rootlets. 



The zoarium is singularly delicate in texture and trans- 

 parent, and the internal structure may be thoroughly 

 investigated with the greatest ease. The endosarc con- 

 sists of a slender thread, running through the tubular 

 stem from cell to cell, and communicating with each 

 through an orifice at the base ; at each division of the 



