270 THE PLANT COVERING OF OCRACOKE ISLAND. 



SAND-STRAND VEGETATION. 



TREELESS, OPEN FORMATIONS. 

 BEACH FORMATION. 



This formation occurs along Pamlico Sound, occupying the flat or 

 gently sloping sandy beach, especially toward the lower end of the 

 island. The species are almost all herbaceous and usually form an 

 open vegetation, leaving much of the soil uncovered. The most 

 abundant is Croton maritimus, which sometimes grows rather closely, 

 excluding other species. By reason of its silvery-gray color, due to a 

 close, stellate, scale-like pubescence, it is one of the most conspicuous 

 plants of the island. It is usually stout and often much-branched. 

 Another noteworthy plant is Physalis viscosa, a perennial herb, with 

 slender roots, sometimes 1.5 meters long, creeping near the surface of 

 the sand, and sending up at intervals short leafy shoots. Its color 

 varies from green to gray with the density of its covering of branched 

 hairs. An interesting feature of this formation is the occurrence in 

 places of diminutive thickets only 1 to 3 decimeters high, composed 

 chiefly of Ilex vomitoria (I. cassine of authors), Zanthoxylon clava- 

 herculis, Juniperus virginiana, with leavesonly of the spreading form, 

 and Opuntia pes-corvi, with its long spines. Among other species 

 belonging to the beach formation, there are of annual herbs Eu- 

 phorbia polygon /'folia, Triplasis purpurea, a canescent form of Sola- 

 tium nigrum, a large-fruited Xanthiuni, and Salsola l-ali, the last 

 being the most abundant; of perennial herbs Teucrium nashii, with 

 slender stolons and white-tomentous lower leaf surface, Chloris 

 petraea, with decumbent culms, rooting at the nodes, Panicum neu- 

 ranthum, and occasionally Capriola dactylon (Cynodon dactyhn 

 Pers.); of woody plants .Rubus trivial is and SmUax bona -nox occur 

 here and there, with prickly steins trailing over the sand. 



DUNE FORMATION. 



Open dunes are occupied chiefly by the handsome sea oats, Uuiola 

 paniculata, the most characteristic strand plant of the Southeastern 

 Slates. The low, rounded dunes which rise from a bare pebbly 

 shingle on the ocean side of the island, and here and therein the 

 midst of the tidal flats, support no other vegetation. The leafy 

 shoots of this grass are produced in great abundance, but flowering 

 branches are much less numerous. 1 Muhlenberg ia filipes is abundant 

 on and among the dunes, its delicate purplish panicles, swaying with 

 the lightest breath of air, presenting a most beautiful appearance. 

 It is almost the only cespitose plant of the island, and grows in 

 tufts that are sometimes 'A decimeters in diameter. Rather small 



■In this respect the Uuiola resembles Ammophila arena ria, which takes its 

 place farther north. 



