1909.] 



NATURAL SCIENCES OF PHILADELPHIA. 



381 



& pure growth (sp. gr. 1.0155) of Baccharis halimifolia (#), which 

 wedges in between the outer strip and the third strip of Spartina patens 

 <(V), which in most places usually succeeds the outer one of the taller 

 salt grass. Along the inner edge of the clumps of Baccharis halimi- 



Plum 

 Island 



*** 



Fig. 1. — Plum Island in Sandy Hook Bay. Dotted areas represent sandy; 

 t , thickets and trees ; ^ , salt marsh ; numerals indicate areas treated of 

 in this paper. 



folia (0) occur pure associations of Su&da linearis (8) and Sali- 

 cornia herbacea (H ), as indicated in the sketch. 



Sand Dune Formation. — Low sandy stretches back of the marsh are 

 covered with typic dune plants, including the marram grass, Ammo- 



