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" Fnfiut.r" In thgf? Dr. Roth is of opinion that the diflepiment does not 



extend wholly acrofs the tube, but leaves it pervious for its whole length. This 



fubdivifion comprifes the genus Conjugata of Vaucher, with Conferva equifeti- 



folia, crifpata, ebenea, vivipara, fucicola, and many others, and it is therefore 



obvioufly far from natural. 



Of the " Toru/ofv," which form the fecond fubdivifion, the diiTepiments rife 

 above the furface of the tube in the form of annular excrefcences. Dr. Roth 

 here fuppofes the diffepimeuts to be interwoven with a large portion of the 

 cellular membrane, which makes them lefs able to refift the elafticity of the 

 enclofed air, and they thereby become diftended. C. flu-viatilis is the only 

 Britifh fpecies that occurs in this fubdivifion, but my obfervations have tended 

 to confirm the opinion of the late lamented Dr. Mohr, that thefe protuberances 

 are of a different nature, and ought not to be regarded as diffepiments. 



C. atra is arranged by itfelf, and forms a third fubdivifion with the name of 

 " Infidtia," the meaning affixed by the Dodor to which term is, that the 

 longitudinal fibres of the filaments on attaining to the length prefcribed for 

 each joint, fuddenly unite in a fingle point, and are bent inwards towards the 

 cavity of the tube, thus forming an appearance fimilar to that of the tortulofa, 

 though in reality of different ftructure ; and hence each joint is narrow at its 

 origin, and gradually incraffated upwards. 



The fourth and laft fubdivifion is compofed of the " Ferticillata," diflinguifhed 

 chiefly by their verticillated, or rather imbricated, ramuli. In this C. vertillata, 

 and fpongiofa are arranged, together with fome foreign fpecies probably of the 

 fame family, and with C. yiilofa, a plant widely different both in its nature and 

 ftructure. 



Having taken this curfory view of the genus Conferva, as eftablifhed by Dr. 

 Roth, it remains only to add, that enough has already been difcovered of the 

 fruaification of many of the fpecies claffed under it, to fhew the neceffity of 

 their removal to other genera, and it feems to me that thofe only mould be 

 retained which arc propagated by feeds formed within the joints, without the 



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