CERAMIACEiE. 213 



branches alternate, bearing a second and third series of 

 branchlets. Favellidia large, lodged at the base of the peri- 

 pheric fibres of the frond near the end of the branches ; 

 tetraspores at the tips of similar fibres. 



In a young state the branches of this plant are dis- 

 tinctly visible to the naked eye, but when mature the 

 whole frond appears to be composed of gelatine, and 

 when taken from the water becomes an undistinguishable 

 mass of pink mucilage, with scarcely any indication of 

 branches, and still less of internal structure. It requires 

 peculiar treatment in drying, and should not be soaked 

 in fresh water, nor subjected to any pressure until the 

 second or third day after it is laid on the paper. It does 

 not present a very promising appearance during the first 

 stage of this process, but the collector must not be dis- 

 heartened, for the result will probably prove more satis- 

 factory than he anticipates. This is a deep-water species, 

 but from its great weight is very liable to be dislodged 

 by the sea, and I have found it in considerable abund- 

 ance in Jersey, either floating, or thrown up on the 

 sands. It is a summer annual. 



Genus XCVIII. CROUANIA. 



Frond gelatinous, single-tubed, jointed, the joints of the 

 stem and branches whorled with numerous, minute, forked, 

 jointed, level-topped branchlets ; "favellidia subsolitary, near 

 the apex of the ramuli, affixed to the base of the whorled 

 ramelli, and covered by them, containing within a hyaline, 

 membranaceous perispore, a subglobular mass of minute 

 spores ;" tetraspores cruciate, large, at the base of the 

 branchlets. — CfiOUAisriA, in honour of the brothers Crouan, 

 of Brest, celebrated among French algologists. 



