CROUANIA. 155 



stance tender and gelatinous. " The structure is very remarkable ; the 

 frond appears to be made up of tufts of fibres radiating from a centre, each 

 tuft, when separated in water under a glass, resembling a double aster or 

 sea-anemone. In the centre of the petal-like fibres are masses of purplish 

 grains." Mrs. Griffiths. 



XXI. CROUANIA. J. Ag. 



Frond gelatinous, filiform, consisting of a jointed, single- 

 tubed filament, whose joints are clothed with dense whorls 

 of minute, multifid ramelli. Fructification: 1, 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 sub-globose 

 mass of minute spores ;" 2, obovate tetraspores of large size, 

 affixed to the bases of the ramelli. Name, in honour of the 

 brothers Crouan, of Brest, celebrated among French Algolo- 

 gists. 



1. C. attenuata, Ag. ; frond capillary, brownish red, gela- 

 tinous, moniliform, much branched ; main divisions sub-di- 

 chotomous, with wide axils ; branches alternate, more or 

 less furnished with ramuli. Harv. Phyc. Brit. t. cvi. Me- 

 sogloia moniliformis, Griff, in Wyatt, Alg. Damn. No. 197. 

 M. attenuata, Ag. Syst. p. 51. Griffithsia nodulosa, Ag. 

 Sp. Alg. ii. p. 136. 



Very rare. Parasitical on Cladostephus spongiosus, at Salcombe, Devon, 

 Mrs. Wyatt. Land's End, Mr. Ralfs. Fronds 1 or 2 inches high, of a 

 brownish or purplish red colour, excessively slender and gelatinous, much 

 branched, all the branches moniliform or resembling strings of minute 

 beads. The branches consist of a single-tubed, jointed filament or axis, 

 from whose joints issue very dense, gltfbular whorls of dichotomously mul- 

 tifid fibres. The joints of the main thread are sometimes short, sometimes 

 of considerable length ; in the former case the globular whorls (or beads) 

 conceal the main thread altogether ; in the latter they are widely separated, 

 and then the plant, under a low power of the microscope, something resem- 

 bles Ceramium diaphanum. Fructification : large tetraspores with pellucid 

 pericarps, resembling those of Callithamnion, seated on the whorled fila- 

 ments, either in pairs, or placed round the branch. I have never seen the 

 favellidia above described, which are given on the authority of Professor 

 Agardh. 



