264 RIVULAKE^E. 



an annual plant, whereas the other exists for several years." 

 Carm. 



A microscopical examination of these two plants will not 

 only make it evident that the two are specifically distinct, 

 but also most probably generically so. 



Section ii. RAPHIDIA Carm. 



Char. Frond gelatinous, subglobose, bullated. Filaments 

 few, flagelliform, simple, moniliform within, scattered 

 through the gelatine, or radiating from a central point. 



1. RAPHIDIA ANGULOSA Hass. 

 Plate LXIV. Figs. 1. 4. 



Char. Fronds gregarious, roundish, gelatinous, hollow, of a 

 bright chestnut colour when recent, changing to dark olive 

 in drying. Filaments large, often produced into a long 

 and curved setigerous point. Sheath broad, often angular. 



Rivularia angulosa Roth, Harv. in Hook. Br. Fl. p. 394.; 

 and in Manual, p. 153. Ulva pruniformis, E. B. t. 968. 

 Raphania nalans Carm. MSS. cum icone. 



Hab. Attached to aquatic plants in ponds and still waters, 

 or floating on the surface, Appin : Captain Carmichael. 

 In a pond on the common east of Lewes and Burwash 

 Road, near Easton Green : W. Borrer, Esq. Swansea : 

 Mr. Rolfs. Cheshunt Marshes : A. H. H. Near Cas- 

 cades, co. Antrim : Mr. Moore. 



" Fronds gregarious, often confluent, one fourth to three 

 fourths of an inch in diameter, roundish, gelatinous, vesicular, 

 and when detached, rising to the surface of the water with 

 the velocity of an air-bubble. Filaments at the distance of 4 

 or 5 diameters from each other, radiating in all directions from 

 the centre of the vesicle ; rising from a colourless globule, 

 inflated for about one-third of their length, thence tapering to 

 a long slender often curved point. Internal mass moniliform, 

 occupying about one half the diameter of the inflated part of 



