392 BIBLIOGRAPHY. 



transversely into four spores, and fixed to a reticulate placenta ; 

 the other containing, in the interior, a mass of round spores, 

 immersed in the middle of a filamentous tissue. 

 Crouan. — Notice sur quelques especes et genres nouveaux d'algues 

 marines de la rade de Brest, par MM. Crouan freres, Pharma- 

 ciens. Ann. S. N. Vol. xii. p. 288. 4 ser. 



Vlvella Crouan, (gen. nov.) 



Frond green, lentiform, 1-2 mill, in diameter, horizontal, ad- 

 herent by the whole inferior surface ; formed in the centre of its 

 surface of round, oval, or angular cells, embedded in a sub-gelati- 

 nous substance, reticulated, and containing some sporidia in their 

 interior. Towards the periphery they become ovoid or rec- 

 tangular, are much smaller, separated from one another, and 

 disposed in radiant lines, simple or forked at their extremities. 

 A vertical section of the frond exhibits the central cellules, ar- 

 ranged in almost perpendicular series, and filled with endochrome. 



This genus (the authors say) resembles, at first sight, under 

 the microscope, the first state of development of the sporidia of 

 Enteromorpha ; but its uniform size at all seasons of the year, its 

 structure, and sporidia, point to its being a new genus of the 

 Ulvacea?. 



Cruoriella Crouan (gen. nov.) 



Frond horizontal, 1-2 centimetres in diameter, adherent by 

 the whole of its inferior surface, of a deep purple, having the ap- 

 pearance of a Peyssonelia, composed of filaments, plunged in and 

 held together by gelatine; the surface exhibiting the lines of* 

 the spherical cellules radiating towards the periphery in the form 

 of a fan. JVematheccd numerous, scattered over the frond, very 

 slightly prominent, formed of simple articulated filaments,, the 

 lower joints very large, spherical, or square, then becoming 1£ 

 times as long as broad, and 3-4 times as long as broad at the 

 summits, which are attenuated, cystocarps immersed in the 

 middle of the nematoid filaments, at the spot where their diameter 

 becomes abruptly diminished, bearing round or square spores, 

 joined end to end, and resembling little heaps, in a simple or cli- 

 chotomous series, fixed together by gelatine. Sphserospores 

 oblong, crucial, attached to the summit of a long articulated pe- 

 dicel, and immersed in the middle of forked and fibrillose filaments 

 constituting the Nematheca. 



This plant, the authors observe, differs in fructification and 

 structure from all known Squamarias. 



Rhododiscus Crouan (gen. nov.) 



Frond, 3-8 mill, in diameter, disciform, of a beautiful rose- 

 carmine, adherent by the whole of its inferior surface, a little 

 thickened in the centre, which is sometimes lifted up and detached 

 from its support ; fining off towards the periphery into a very 

 delicate, fan- shaped, lobed membrane, sometimes laciniated, and 

 presenting on its surface dichotomous series of ovoid or angular 



