BATRACHOSPERME.E. 293 



" The articulations, or internodes, may be compared to reversed cones, 

 the superior part or whorls being formed of a few short, simple subu- 

 late filaments, which are not beaded ; in these filaments the colouring 

 matter chiefly resides, and it is amongst them that the glomerules are 

 formed ; that portion of each articulation which is below the whorl is 

 transparent, and beautifully exhibits the tubular and jointed structure 

 of the layers which invest the primary cells in all the species of the 

 genus Batrachospermum ; from many of these tubes short branches are 

 given off, which have almost the appearance of scales." Hassall. 



var. Dillenii. Bory. Ann. de Mus. xx., t. 22, f. 2. 



Filaments dark brown, very thin, lower nodes remote, the 

 interstices beset very densely with prominent cells, upper nodes 

 crowded, branchlets very short, consisting of 3-4 cellules, ex- 

 treme apical nodes confluent. 



SIZE. Cellules *012 mm. diam. 



Lemanea Dillenii, Bory. Ann. de Mus. xx., 23. 



Batrachospermum vagum, e. Dillenii, Rabh. Alg. Eur. in., 

 407. 



Conferva fontana nodosa, lubrica, nigris, Dill. Muse. t. 2, f. 

 46. 



This is usually considered as a variety of B. vagum, but it seems more 

 closely allied to B. atruni, if that be really a distinct species. 



Plate CXXVI. fig. 2. Portion of filament X 200 diam. 



GENUS 120. THOREA. Bory. (1808.) 



Thallus filamentose, attenuated at the apex, branched, purple- 

 brown, villose, mucous, with a solid central medullary stratum, 

 surrounded by dichotomously divided branchlets. Surun genre 

 nouveau de la Cryptogamie aquatique, nomme Thorea. 



Thorea ramosissima. Bory Ann. Mus. xx. 127. 



From a hand's-breadth to a foot long, and rarely two feet, 

 very much branched, about the thickness of a horsehair, dark- 

 green, of a beautiful purple-violet when dry, ramelli spreading 

 horizontally, long and short alternating, articulate, joints 1-3 

 times as long as broad, or twice that length. 



Harv. Man. 120. Hass. Alg. 65, t. 16, f. 3-4. Rabh. Alg. 

 Eur. iii. 



Batrachospermum hispidum, De Cand. Fl. Fr. ii., 60. 



Attached to wood, &c. Walton-on- Thames. 



Plate CXXVIL fig. a. Small plant> natural size ; b, ramuli and spore ; 

 C> portion of filament X 400* 



