authority of fpecimens fcnt from Profeflbr Mertens to D, Turner, I have felt no 

 hefitation in uniting with the prefent, nor can I fee fufficient grounds to defcribe 

 them even as feparate varieties. 



The diffepiments are a little contracted, and generally quite colourlefs j but, 

 before the plant is expofed to the air, or the juices at all collapfed, they on the 

 contrary appear darker than the other parts of the filaments, the joints are cylin- 

 drical, and of a deeper color towards their extremities ; their length, though fub- 

 je£t to fome variation, even in the fame branch, is feldom lefs than double their 

 width. 



Dillenius's " Conferva fluviatilis trichodes, extremitatibus ramofis," which moft 

 authors have followed Hudfon in making a variety of this plant, appears to be a 

 diftincT: fpecies: — it is the Ceramium afperum of Dr. Roth. In drying C. 

 rupeftris retains its beautiful green color ; but the joints contract alternately in a 

 curious manner, as figured in the Catale&a Botanica : — it adheres to neither glafs 

 nor paper. 



A. C. rupeftris, natural fize. 



B. Ditto, magnified 3. 



C. Ditto, 1. 



