5cm. 



-500ft, 



FIG. 366. Zonation about a pond 



I, pond ; II, bog zone ; III, swampy thicket zone ; IV, incomplete zone in arid soil 

 of a sand pit; V, dry meadow zone; VI, dry woodland zone ; a, floating mass 

 of Eriocaulon ; b, deepest area in pond, six to ten feet; c, association of tall 

 rushes (Juncus militaris) ; d, birch woodland (Betula populifolid) ; WE, line 

 intersecting formations of west side of pond ; SN, line intersecting forma- 

 tions of north end of pond 



476 



