_^70 THE PLANT COVERING OF OCUACOKE ISLAND. 



SAND-STRAND VEGETATION. 

 TREELESS, OPEN FORMATIONS. 

 BEACH FORMATION. 



This forination occurs along Pamlico Sound, occupj'ing 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, Avith 

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

 the sand, and sending up at intervals short leaf}' 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 onl}" 1 to 3 decimeters high, composed 

 chiefly of Ilex vomHoria {I. cassine of. authors), Zanthoxylon cJara- 

 herculiSy Juniperus virginiana, with leaves only 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 En- 

 pliorhia polygonifoUa, Triplasis purpurea, a canescent form of Sola- 

 num nigrum,, a large-fruited Xanthium, and Salsola kali, the last 

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

 slender stolons and white-tomentous lower leaf surface, Chloris 

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

 ranthum, and occasional!}' CaprioJa dactylon {Cynodon dadylon 

 Pers.); of woody plants Buhus trivial is and Smilax boua-iwx oecnr 

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



DUNE FORMATION. 



Open dunes are occupied chieflj^ b}' the handsome sea oats, Uniola 

 paniculata, the most characteristic strand plant of the Southeastern 

 States. The low, rounded dunes Avhich rise from a bare pebbly 

 shingle on the ocean side of the island, and here and there in the 

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

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

 branches are much less numerous.^ Mulilenhergia filipes is abundant 

 on and among the dunes, its delicate purplish panicles, swaj-ing with 

 the lightest breath of air, ]3resenting a most beautiful appearance. 

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

 tufts that are sometimes 3 decimeters in diameter. Rather small 



' In this respect the Uniola resembles Ammophila arenaria, which takes its 

 place farther north. 



