SERTULARIA. 



unlike the outward appearance of the Gorgonias, fuch as 

 the Sertularia verticillata, or Horfe-tail Coralline; the 

 S. fpinofa, or Silk Coralline ; the S. halecina, or Her- 

 ring-bone Coralline ; and the S. frutefcens, or Shrubby- 

 Coralline ; thefe feem to form the firft or leading ftem as 

 a fupport for the next to climb up, fo that in fome old 

 ftems, -particularly of the Herring-bone Coralline, I have 

 obferved the inner tubes of their ftems have been rotted 

 and deftroyed, by being inclofed by fo many others on 

 their furface. See page 18, Effay on Corallines. 



Some writers feem at a lofs to account for the growth 

 of thefe kind of Sertularias, whofe ftem and branches are 

 thus compofed of many capillary tubes, and therefore are 

 of opinion, that their manner of vegetating is obfcure, 

 and that probably they grow not only in length and 

 thicknefs, but likewife in fubftance and number of tubes, 

 as plants do. 



In order to account for the tubes flicking toge- 

 ther, they fuppofe that they are provided with an in- 

 termediate fubftance, by which fome are flightly glued 

 together, others rendered more compacl:, and fome even 

 become folid and hard. 



But it appears evidently on examination, that this ge- 

 latinous fubftance is common to all the genus, and is no 

 other than what the radical parts of them all poffefs in 

 common, in order to adhere firmly to their feveral 

 ftations. 



So that inftead of thefe radical tubes lying horizontally, 

 and adhering in lines like the Sertularia pumila, or Sea-oak 

 Coralline, on its fucus, and many others after the fame 

 manner, they raife themfelves up from their bafes (where 

 thefe little tubes are firft fixed) and fupport one another 

 by this natural gluten in an erect form, making a ftem 



F 2 out 



25 



