the Brttijh Fuc/\ -with particular Defer iptions of each Species. 141 



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

 accordingly refers to the descriptions of both of them indifferently. 

 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 diftinclion : the fquarenefs or roundnefs of 

 the rib or nerve when it becomes inverted with the membrane. 



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

 tetragonus is met with in the Ifle of Man, where teres does 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 eaft 

 and weft, where tetragonus has no place. 



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

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

 prefled 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 fomewhat carti- 

 lagineous— in teres they are membranaceous. Tetragonus is found 

 growing above the low-water mark — teres 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, Rector of Aber near Bangor, for his apprifing us of the 

 differences between thefe two fpecies. 



Gmelin with his ufual fagacity fuppofed tetragonus to have a 

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

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



frond. 



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

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

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

 is not dift in gui friable from tetragonus. 



Bauhin's 



