Snu'//i : No/cs on Ihc Vcirclation of Ponds. 395 



For some reason this pond has dried up. Wliether this is due 

 to gradual raising of the bottom, or to the deepening of the out- 

 flow so that it drained the pond to the bottom, or to leakage, we 

 cannot say. The vegetation has interesting features. Near 

 the centre are patches of two water-plants — the Pondweed 

 {Potaniogeton) and Bur-reed {Sparganucni) — restricted to what 

 are now the wettest spots. The Pondweed has small reddish 

 leaves with short stalks, the Bur-reed has short narrow leaves ; 

 unfortunately specimens were not taken for identification. Both 

 are land-adaptations, and are probably the remains of the original 

 aquatic vegetation which has been displaced. The other con- 

 spicuous plants of the pond-hollow are : [a) Water Sweet-grass 

 {Glycerin aquatiai), occup)ing the centre ex::ept the parts utilised 

 by the Pondweed and Bur-reed ; {b) Iris pseudacorus at the southern 

 or inflow end ; (r) Marsh Horsetail [Equisetuni palnstre) at the 

 northern or outflow end ; {d) a broad marginal zone of Rushes. 

 The large patch of Water-grass indicates the part of the hollow 

 which is occasionally under water. It is a feature of this grass 

 that it grows well in a moist place liable to inundation. The 

 Iris and Marsh Horsetail occupy well-defined areas, and both 

 are typical marsh plants. Altogether the vegetation of this 

 hollow indicates that it is moist, and even marshy at times, but 

 is never long under water. 



Other examples of dry ponds were found. In one extreme 

 case a clump of Rushes in the centre was the last remnant of 

 marsh vegetation, the other plants being intruders from the drier 

 knolls. 



The ponds at Filey are thus instructive examples of aquatic 

 and marsh vegetation. The ponds themselves show every stage 

 of transition from ponds oi open water to marshy hollows, and 

 even dry hollows. The vegetation includes examples oi the 

 chief biological groups of aquatic and marsh plants, which may 

 be summarised as follows : — 



(i) Floating plants, e.g., Duckweeds. 



(2) Plants rooted in mud, with floating or submerged leaves, 



e.g., Pondweed and Water Parsnip. 



(3) Plants rooted in mud, with leaves which rise above the 



surface of the water. The most successful social species 

 are those with long erect leaves, e.g., Bur-reed, Iris, 

 Water-grass, Rushes, and Sedges, and with these the 

 two Horsetails may be included. The Water Dropwort 

 is an example of an Umbellifer which, instead of the 

 broad cut-up leaves of that order, has adopted a narrow 



1903 October i. 



