Nov., 1910.] A Floristlc Survey of Orchard Island. 209 



The society forms a narrow interrupted border, not more 

 than 4 feet wide of mature fruiting but not tall Hibiscus moscheu- 

 tos. Of the secondary species the Hypericum is quite abundant 

 at the outer margin of the eastern portion of the zone. The other 

 species are very sparse, of the Xanthium and Rosa there is but a 

 single plant. 



9. Polygonum-Scirpus society. 

 Facies. 



Polygonum emersum. Scirpus fluviatilis. 



Secondary species. 



Typha latifolia. Roripa palustris. 



Cyperus strigosus. Roripa americana. 



Ilysanthes gratioloides. Alisma plantago. 



Hypericum mutilum. Amaranthus hybridus. 



Polygonum pennsj'lvanicum. Arctium minus. 



Polygonum acre. Acer rubrum seedling. 



Agrostis perennans. Ulmus americana seedling. 



Gratiola virginiana. Hibiscus moscheutos seedlings. 



Erechtites hieracifolia. Cladophora sp. 



Echinochloa walteri. Scirpus lacustris. 

 Eupatorium purpureum. 



This society is 40 feet wide, with the entire surface exposed 

 at the present low water level. Hence the extremely hetero- 

 genous collection of plants among the secondary species. Dead 

 Typha latifolia stalks are so abundant in the western portion of 

 the zone as to warrant considering it a dominant plant; but the 

 Typha is not at all abundant in the eastern portion of the zone. 

 Arctium minus and Alisma plantago growing close together illus- 

 trates strikingly the submerged and emersed stages of the society 

 and the rapidity with which a new habitat is adopted by 

 plants. That the ground has been recently exposed is evidenced 

 by the fresh masses of Cladophora. 



10. Scirpus lacustris society. This is a fringing zone 40 

 feet wide and extending only about half way across the belt, the 

 surface is partly emersed. There is a 20 foot wide sandy beach 

 scantily clothed with the Scirpus. 



Secondary species. 



Potamogeton natans. Potamogeton sp. 



Potamogeton pectinatus Nelumbo lutea. 



11. Nelumbo lutea society. A small bed of Nelumbo lutea 

 borders the Scirpus lacustris society to the N. N. E. The 

 leaves are but few and widely scattered. 



Fifteen feet east of the belt is a public dock, 4 feet wide and extend- 

 ing 7S feet out into the water and .54 feet up onto the shore. The 

 marsh zones are not formed immediately on either side of the 

 dock. On the upper portion of the beach close to the dock, the 



