the Brilljh Fud, -with particular Dtfcriptkm of each Species. 141 



term efcukntus ; for Linnaeus regarded them both as the fame, and 

 accordingly refers to the dcfcriptions of both of them indifFevently. 

 However, there are fo many differences obfervable in them that we 

 have ventured to feparate them, and have named them from the 

 leading mark of their diftindlion : the fquarenefs or roundncfs of 

 the rib ornerve when it becomes inverted with the membrane. 



In the firft place, they are not found in the fame place : the 

 ietragoniis is met with in the Iflc of Man, where teres docs not make 

 Its appearance ; teres is found in the Ifle of Anglefey, and in many 

 places on the northern coafts of England and Scotland both eafl: 

 and weft, where tetragonus has no place. 



Tetragomis has a fquare ftalk or rib — teres a roundifh one ; tetrago- 

 nus has the bafe of the frond rounded and fub-cordate, as is ex- 

 preffed in Gmelin's figure— teres has it very much attenuated, as 

 may be feen in Mr. Lightfoot's reprefentation. In tetragonus the 

 little leaves at the bafe of the frond are thick and fomcwhat carti- 

 lagineous— in teres they are membranaceous. Tetragonus is found 

 growing above the low-water mark— /^r^i always juft within the 

 low-water mark. Tetragonus is by far the greater. 



We are much indebted to our valuable friend the Rev. Mr. 

 Davies, Rcftor of Aber near Bangor, for his apprifing us of the 

 differences between thefe two fpecies. 



GmeUn with his ufual fagacity fuppofed tetragonus to have a 

 fibrous root; but his draftfman unfortunately has made it a folid 

 one. There is an omiffion alfo of the leaves at the bafe of the 

 frond. 



Mr. Lightfoot, who met only with teresy defcribes it with a fquare 

 rib. He was led into this error moft probably from examinino- only 

 dried fpecimens : in drying, the ftalk becomes flat, and in that ftate 

 is not diftinguifliable from tetragonus, 



Bau bin's 



