A SURVEY OF THE LOWER. TEES MARST-TF.S 97 



(i) THE AQUATIC FORMATION. 

 The Upper Lode provides us with a closed shallow water 

 association of no great complexity for, probably owing to 

 repeated efforts to clear it, rendered nugatory by the small 

 fall and consequent stagnant nature of the water, we find 

 generally an association of the following* composition domi- 

 nated by Lemna minor and L. trisidca : — 



Lemna minor cd Apium nodiflorum 



L. trisulca cd Nasturtium officinale f 



Scirpus lacustris f N. sylvestre r 



Callitriche spp f Alisma plantago-aquatica ... 



Phragmitis vulgaris Id Potamogeton pusillum 



The Reed Swamp. 



Following this, and isolated from it by an embankment (the 

 vegetation of which will be considered below), we encounter a 

 reed swamp association of a well developed type occupying a 

 band of varying width throughout the length of the "bog." 

 Viewed from the slope to the north, this Phragmitis transition 

 association seems to bear the aspect of a sharply defined 

 homogeneous community — a view not inconsistent with the 

 facts to a large extent. Closer examination, however, 

 demonstrates that fairly successful attempts have resulted in 

 the infiltration of forms, more at home in the typical marsh 

 associations, even to the very midst of the association in its 

 purest form. 



Whilst Phragmitis vulgaris remains dominant throughout, 

 the debatable border between the attacking marsh and the 

 (probably) decadent reed swamp seems more properly to 

 appertain to the marsh, and will be treated as an integral 

 portion of such. 



As one examines this swamp, one cannot but wonder at 

 the marvellous way in which Caltha palristris and Ramui- 

 ctdus Ficaria complete their life history before the reeds 



* The symbols for frequency are : — d, dominant ; sd, sub-dominant ; 

 cd, co-dominant ; f, frequent ; o, occasional ; a, abundant ; r, rare ; vr, 

 very rare ; la, Id, Isd, etc., locally abundant, locally dominant, locally 

 sub-dominant, etc. ; rr, rather rare. 



G 



