334 



BOTANICAL SURVEY OF DISMAL SWAMP REGION. 



The lesser dunes on this coast appear usually to originate about 

 tufts of marram grass (Ammophti-a areuaria), although Uuiolapani- 

 culata, Punicum amarum, and oilier plants arc likewise effective as 

 the nuclei of accumulations. As a rule the outermost dunes are the 

 lowesl, being only breast high or lower. The height of the hills 

 increases with greater or less regularity to the innermost, normally 

 the highest, line of duties. The iasl are often forested, although at 

 Cape Henry, where they attain their maximum elevation, they are 

 devoid of vegetation excepting a few plants of marram grass (Ammo- 



Fio. 53. — Incursion of the sand on inland vegetation near Cape Henry, Va. 



pJti/ti arenaria). The outermost, and innermost dunes usually form 

 regular chains, broken here and there by the wind, but conforming 

 mainly to the conlour of the coast. The middle dunes also exhibit a 

 tendency <o form rows parallel to the shore line, but this tendency is 

 often modified and obscured so that there frequently appears a total 

 lack of order m their arrangement. The outer or seaward slope of 

 the dunes is very gentle, and is usually more irregular than the 

 abrupt- landward declivity, whose angle, e. g. , in the highest dunes at 

 Cape Henry, is about MS degrees. 



At and near Cape Henry the dune area is unmistakably advancing 



