I58 OHIO STATE ACADEMY OF SCIENCE. 



the life of an aquatic crown-former. The Decodon zone is almost 

 entirely wanting at the south end of the lake, having been 

 recently destroyed as stated before. It was very perfect here 

 formerly, as appears in Fig. 1, and at the south-east it is still 

 very wide. On the west side the zone is rather narrow, being 

 only about fifteen feet wide. 



Other plants in this zone are : 



Alisma plantago L. Ranunculus abortivus L/. 



Sagittaria latifolia Willd Roripa hispida (Desv.) Britt. 



Scirpus lacustris L. Naumbergia thyrsiflora (L. ) Duby. 



Carex comosa Boott. Cicuta bulbifera L,. 



Iris versicolor L. Cephalantbus occidentalis L,. 



The Cephalanthus is here and there an invader from the out- 

 side and will finally establish a new shrub zone because of the 

 changed conditions produced by cultivation of the surrounding 

 hillsides. Had the lake remained in its natural condition sur- 

 rounded by dense forest the progress of the zones would probably 

 have been gradual and continuous, but as it is there will be from 

 time to time comparatively sudden advances, thus producing con- 

 fusion in the established order of the old societies. 



Uliginous Zone. The distinctive peculiarity of this zone 

 is the presence of various species of Carex, Eleocharis and Scirpus, 

 together with Equisetum fluviatile L., which is very abundant in 

 some places. Besides these there are a number of other moisture 

 and mud-loving species. This zone is intercalated on the east 

 and west sides where wide mud flats have been formed between 

 the Decodon and shrub zones. It is very prominent on the east 

 side where there has been much filling in from the cultivated 

 field beyond. The zone is absent at the north where there has 

 been no such filling and was probably also absent from the south 

 end when natural conditions still prevailed. In the moister parts 

 the Equisetum, Eleocharis and Scirpus are characteristic, while 

 in the outer, dryer margin the various species of Carex form a 

 thick sod in which occur a number of uliginous herbs. Some 

 isolated pioneers among the shrubs, especially Cephalanthus, 

 have also taken a foothold on the east side although still few 

 in numbers. On the west side the zone has been much invaded 

 and is now in a transition state, progressing rapidly toward 

 a thicket and forest society. 



