PRACTICAL STUDY OF PLANT FORMATIONS. 635 



point on the land these are in succession: white pine (i), oak (2), willows 

 (3), thoroughwort (4): littoral zone of semi-aquatics, typha (5), bulrushes 

 (6), arrow-leaf (7); mid zone, pond-lilies and potamogetons (8); Sub- 



Land Zone. 



Littoral Zone. 



'.Mid Zone. 



Submerged Zone. 



mm 



bo oo oooooo 

 % o ooooooo 

 oo ex o o o o of 

 ooo o ooooo 



Willow Formation 

 (Salicetum). 



Eupatorium 



Formation 



(Eupatorietum). 



Typha Formation 



ypha F< 

 (Typh 



.etum). 



1 Bulrush Formation 

 (Scirpetum). 



Arrow-leaf Formation 

 (Sagittarietum). 



\ Pond-lily Formation 

 (Nymphetum). 



j. Pondweed Formation 

 | (Potamogetonetum). 



Bassweed (Chara) 



Formation 

 (Charetum) 



Fig. 535- 

 Chart showing relative position of plant formations in zones along lake shores. 



merged zone, pond weeds (Potamogeton and Vallisneria, 9), bassweed 

 (Chara, 10). By the side of this, on the same shore, the typha is replaced 

 by sedges, and the arrow-leaf by the yellow water-lily or spatter-dock (Nu- 



