230 BRITISH SEA-WEEDS. 



Callithamnion thuyoideum. The cypress Calli- 

 thamnion. 



Fronds growing in tufts, from one to three indies long; 

 branches alternate, spreading, those at the base of the frond 

 longest, the rest becoming gradually shorter ; plumules al- 

 ternate, triply pinnate, borne on each articulation of the 

 branch, the first being always on the upper side of the 

 rachis ; articulations of the stem and branches variable, of 

 the plumules uniformly about twice as long as broad. 

 Favellse solitary or in pairs, on the stems of the plumules ; 

 tetraspores tripartite, minute, on the tips of the ultimate 

 series of pinnules. 



This is another very beautiful and too rare species. 

 It grows on rocks near low-water mark in spring and 

 summer, and is annual. Several localities on the south 

 coast, Yarmouth, Swansea, and the western shores of 

 Ireland, are its recorded habitats. Its colour is bright 

 pink, and its mode of growth very compact. 



Callithamnion gracillimum. The very graceful 

 Callithamnion. 



Fronds growing in tufts, one to four inches high, very 

 slender, irregularly branched ; main branches few, simple, 

 with an ovate outline, attenuated at the point ; the lower plu- 

 mules short, pinnate, the upper long, lanceolate, thrice pin- 

 nate; all the divisions alternate. Favellre roundish, or irre- 

 gularly lobed, near the base of the plumules ; tetraspores 

 minute, on the tips of shortened pinnules of the plumules. 



This very elegant species is extremely rare ; it was 

 first found in this country by Mrs. Grifi&ths, growing on 

 the mud which covers the base of the pier at Torquay, 

 and was subsequently gathered at Milford Haven and 

 Falmouth. It is annual, and attains perfection in 



