Jennings : A Botanical Survey of Presque Isle. 



381 



Fades. — 



Scirpus americaniis. 



Principal Species. — 



Scirpus validiis, 



Typha latifolia. 

 Bid ens cernua. 



Secottdary Species. — 

 Cicuta bulbifera, 

 Sagittaria latifolia, 

 Riimex altissimus, 



Iris versicolor, 

 Sparganittin eurycarpum, 

 Lemna minor, 

 Nostoc sp. 



The Bidens cernua society determines during late summer the only 

 conspicuous aspect of the formation. Cicuta bulbifera in places attains 

 to considerable importance, but is never very conspicuous. In the 

 Typha latifolia consocies the Sparganiuin shows a strong tendency 

 towards the segregation of a secondary zone on the shoreward side of 

 the formation in water even shallower than that occupied by the Typha. 



The Carcx-PIiraguiites Formation. 



The outer bank of the pond Z has just outside of the Typha-Scirpus 

 formation a zone occupied by grasses and sedges and extending from 

 the wet bank of humus just above the water's edge into the pond to 

 a depth of three to four inches. There is, however, considerable fluc- 

 tuation in the water-level of the pond, and during periods of heavy 

 rainfall the whole habitat is often inundated. 



The structure of the formation is as follows : 



Fades. — 



Carex stricta angustata. 



Principal Species . — 

 Aster novce-afiglicB, 



Secondary Species. — 



Scirpus americatius, 

 Dryopteris thelypteris, 

 Panicularia nervata, 

 Carex hystricina, 

 Carex aquatilis, 

 Carex tnuhlenbergit, 

 Galium aparine, 



Phragmites phragmites. 



Zizania aquatica. 



Scirpus fluviatilis, 

 Calamagrostis canadensis, 

 Dulichiujn arundinaceum , 

 Carex lanuginosa, 

 Carex prasina, 

 Naumbergia thyrsi flora , 

 Scutellaria lateriflora. 



Scutellaria galericulata. 



