1902] THE ECOLOGY OF THE DELAWARE COAST 2QI 



4 



germinate, and such plants as Cakile sp., Salsola Kali, Xanthiimt 

 sp., and Atriplex areiiaria are found. Here also we find tufts of 

 Ammophila arejiaria [A. ancndinaced), although it is not a char- 

 acter plant. This succulent zone is in some places confined to 

 the ridge of debris around the bases of the low dunes, in others 

 it extends much further back. It may reach many feet inland, 

 to the foot of the higher dunes, or may even form channels by 

 which the sea enters inland lakes in times of storm. The name 

 of the zone indicates the structure of two of the characteristic 

 species, Cakile and Salsola, and of the rarer Atriplex. 



(ii) Low Ammophila dune zone. — From the line of summer 

 driftwood to that of winter driftwood has been called by Dr. 



Cowles'5 "middle beach," while above the winter drift line the 



"upper beach" extends to the foot of the dunes. Here condi- 

 tions are different. The winter drift line usually lies at the foot 

 of the higher dunes, although logs are sometimes found on the 

 low dunes. Hence there is no "upper beach" corresponding to 

 that on the Lake Michigan strand, but what corresponds to the 

 *' middle beach " is more or less distinctlv divided into two 

 zones, which are designated here as "succulent zone" and *'low 

 Ammophila-dune zone." As the name indicates, the upper belt 

 is characterized by low dunes held by Ammophila arciiaria, in 

 association with Panicum amariiui and Cenchrus tribiiloides, while 

 scattered mats of Euphorbia poly gonifolia and bunches of Oenothera 

 hiimifusa occur. Xanthium comes up from the lower zone in 

 places, and Leptilon ca?iadense {Erigero?i ca?iade?isis) wanders to 

 some extent from the higher dunes. From the fact that the 

 winter drift line lies back of these dunes, it seems probable that 

 they are of annual formation. This question was not settled 

 definitely, but in July they appeared to be rather large and firm 

 for spring planting. North of Rehoboth the succulent zone is 

 very narrow or entirely wanting. The beach is wide and bare 

 and slopes to the first ridge of dunes, the low Ammophila-dune 

 zone being omitted, or no distinction appearing between it and 

 the next belt. At the Cape the same conditions obtain, the 



^Loc. cit. 115. 



