THE VEGETATION OF SHACKLEFORD BANK 23 



are required to hold it in place and, by the addition of humus, to fur- 

 nish the conditions necessary for a pennanent plant covering. Of these 

 species, by far the most valuable in this locality are Spartina patens (S. 

 juncea) and Physalis vkcosa. The latter possesses the toughness of 

 leaf necessary to resist the driving particles of sand, and has, in addi- 

 tion, very long, slender, tough, branching root-stocks, which are admir- 

 ably adapted to hold in place the sand throughout a considerable area 

 around each individual plant. In one plant one of the root-stocks, not 

 including the branches, was found to be upwards of 45 feet in length. 

 Furthermore, Physalis is a perennial plant which sets seed freely. Spar- 

 tina patens possesses the same advantages, although the root-stocks are 

 not so long, and is, in addition, more able to resist adverse conditions. 

 The other species which flourish on more or less unstable sand, such as 

 Euphorhia polygonifolia, Croton punctatus, Cenchrus trihuloides, and 

 others, are not so valuable as sand binders, because they lack the exten- 

 sive branching root-stocks of the two species mentioned first, and because 

 the majority {Croton punctatus is an exception to this rule) are annual 

 plants, which are useful only in the summer. One shrubby plant, Iva 

 oraria, would prove valuable if it could endure the severe conditions 

 obtaining on sandy areas exposed to the full sweep of the wind; this 

 has not yet been demonstrated. Figure X, B, shows this species forming 

 a stable dune where it is somewhat protected from the wind. Another, 

 Ilex vomitoria, is an efficient sand binder and an excellent windbreak 

 when it once gets a foothold. It is difficult to transplant, however, and 

 it is somewhat doubtful whether it would grow from seed in exposed 

 sandy localities. If any reclamation operations are undertaken, efforts 

 should be made to establish it on the exposed sand. 



GEOGRAPHICAL DISTRIBUTION OF SHACKLEFORD PLANTS 



The entire chain of sandbanks along the JN'orth Carolina coast lies 

 in the Austro-riparian area of the Lower Austral Zone.i This area in- 

 cludes the coast region beginning from the mouth of the Chesapeake 

 Bay and the coastal plain region of the South Atlantic and Gulf States 

 from North Carolina to Texas, with the exception of the southern ex- 

 tremity of Florida. An analysis of the flora of Shackleford shows the 

 Austro-riparian element to be dominant at this place. Over 24 per cent 

 of the total number of plants listed are characteristic of the flora of thii 

 area. These are as follows : 



iSee Merriam, The GeoRraphical Distribution of Animals and Plants in North America: Year 

 Book, U. S. Department of Agrieultme, 1894, pp. 203-214. Also. Life Zones and Crop Zones of the 

 United States, Bull. 10. Biol. Survev. 1898. 



