10 



Roth fup7 >f-:s that the joints are in fact a ferios of annular feed-cafes, not 

 attached to, but difpofed within the filaments, at regulaT fhort intervals from 

 each other •, and that thefe intervals conftitute the fuppofed ditTepiments. This 

 fubdivifion comprifo Vaucher's natural genus Ofci/latcria, and is the fame with 

 the feclion 13. a. of my fynopfis, but I have not ufed the word fpsrangium, be- 

 caufe it cannot be properly applied to thefe joints, as will be hereafter fhewn. 



Of the fecomi fubd'vifion, which is entitled, " Utiicutis matrkalibus" Dr. 



Roth fays, that this fpecies of fpurious partition differs from thofe formed by 



the annular fted-cafcs above defcribed, in this particular, that they are not 



vifible in the earliclt, but only at fome advanced ftage of their growth, or in 



confequence of fome violent concuffion, and that the joints can never vary 



from the pofition allotted to them. Whilft the plants are young, or till their 



organization has been difturbed, the internal veficles are contiguous to each 



other at their extremities, and the filaments then appear in every refpect equal 



and continuous ; but, when at length -thefe veficles become contracted, an 



empty pellucid fpace is left at each extremity, without any appearance of a true 



diflepiment in the middle. The kind of joint here defcribed is found, according 



to Dr. Roth, in many of the Ceramia, as well as in C. tegagrophila, er'iceto urn, 



and other Confervx without any natural aflinuy ; and it appears to me evident 



that the term utriculus mdfricalis cannot with propriety be ufed to define a 



fpecies of joint which occurs fo frequently in capfuliferous fpecies. 



The plants of the third fe&ion, " S/riSltt/is," are deflitute of real joints, but 

 divided by annular flrictures at uncertain diftances from each other. C. torulofa 

 is the only Britifh fpecies here arranged, unlefs my fufpicion fhould prove well 

 founded, that Dr. Roth's C. reptans is Fucus opuntia. 



We next come to the third main divilion of the filamentous Confervse, 

 " Ai tlcuhitit gen'culis veils." Such alone are admitted by Dr. Roth to be true 

 difleplments as actually iitterfecT: the interior of the tube, being formed by the 

 branching of the parallel fibres, of which, together with a cellular membrane, 

 the filament itfelf is compofed. This fetlion has four fubdivifions, of which 

 the firft is the 



