164 OHIO STATE ACADEMY OF SCIENCE. 



to the lake shore, in a comparatively short time the societies 

 become disturbed and may make sudden advances without defin- 

 itely occupying the intervening ground. 



The final result of the filling of the lake and the progression 

 of the zonal societies will be a moist mesophytic forest. Near 

 Brush Lake there are many small swamps and ponds, in various 

 stages of destruction, which show quite strikingly what the 

 actual history with any given set of conditions will be. If the 

 filling is slow and uniform, the final stage before the hydrophytic 

 forest is a swamp, shrub society. In these swamps the same 

 shrubs mentioned above as occurring in the shrub zone of Brush 

 Lake are the predominant vegetation. Cephalanthus, various 

 willows, dogwoods, and swamp roses take possession and these 

 are followed by the silver maple, white elm, white and red ash, 

 black and peach-leaf willow, and other trees. 



There is an interesting extinct or nearly extinct pond about 

 three-fourths of a mile north of Brush Lake on rather high 

 ground in a small, unpastured forest. A ploughed field extends 

 near one side which has evidently been responsible for some rapid 

 filling in recent years. The fringe of hydrophytic shrubs is still 

 near the margin and just outside of this is a young and very 

 thick zone of white ash. The whole centre inside of the shrub 

 zone is an open, flat, nearly circular area with a small depression 

 in the centre about ten feet across. During dry seasons the water 

 disappears entirely and the area is covered with rank moisture- 

 loving weeds, while in a wet season it is covered with water sev- 

 eral feet deep. 



In the fall of 1902, Nymphaea advena Sol. was present in 

 the small depression in the centre, although the leaves were 

 mostly dry. No pond lilies were evident outside of this depres- 

 sion, although the area was carefully searched. Along with the 

 Nymphaea and around it was an abundance of Polygonum 

 punctatum Ell., and surrounding this was a dense growth of 

 Polygonum hydropiperoides Mx. The last mentioned plant 

 extended outward to the shrub zone. But at some distance from 

 the centre the Polygonum was intersperced with very tall plants 

 of Erechtites hieracifolia (L.) Raf. and other moist ground 

 weeds as — 



