(12) 



numerous, more slender and setaceous, and often forked and compressed. 

 Mixed with the branches on the main stem are often to be observed 

 " small linear, simple or forked, narrow compressed leaves, furnished with 

 a midrib, and much attenuated towards the base and summit." Air-vessels 

 are immersed in the ultimate branchlets, generally near their base ; they 

 are elliptical, rather large, single or in pairs, and are generally of a paler 

 colour than the rest of the plants. Substance very hard and woody in 

 the older parts, more tough and leathery in the younger, but not at all 

 adhering to paper. Colour, a bright greenish olive, almost black when 

 dry. Receptacles terminal, long, slender, linear or linear-lanceolate, 

 beset with long, slender, setaceous spines. 



All the species of Ci/stoseira seem to be ocean species with us, none of 

 them being found either on the east coast of England or Scotland, and 

 but rarely on that of Ireland, preferring those shores which are washed 

 by the waters of the "broad Atlantic" to those laved by the German 

 Ocean or the Irish Sea. 



The present species is by no means an exception, as it is recorded as 

 having been found all round the Irish coast, except on the eastern shores 

 of the island, and we are not aware of any recorded habitat on the eastern 

 shores of Great Britain. 



It is one of the largest and handsomest of the genus, often growing to 

 a length of several feet, and its long, slender branches, with their densely- 

 tufted brush-like summits waving gi-acefully in the swell, " are exceed- 

 ingly beautiful." 



From the other species of the genus its long, slender receptacles 

 readily distinguish it. These are often nearly an inch in length, and 

 when young covered with setaceous ramuli, but when old these dis- 

 appear, and the receptacles are nearly smooth. 



EXPLANATION OF PLATE CXXXIV. 



Fig. 1. — Cystoseira fibrosa, natural size. 

 2. — a, receptacle; i, vesicle. 

 3. — Leaf-like spine. 

 4. — Section of conceptacle. 

 5. — Tuft of antheridia. All magnified. 



