870 



BOTANICAL SURVEY OF DISMAL SWAMP REGION. 



CakUe edentula and Salsola kali, both sueculenl animals, attain 

 their besl development on the exterior line of dunes. The former, 

 especially, sometimes forms large mats, with decumbent branches as 

 much as 9 decimeters (3 feet) long and a strong taproot penetrating 

 vertically into the sand to a maximum depth of 2 feel (6 decimeters). 

 A stout, low-stemmed Xanthiuin ' was observed only at Cape Henry, 

 where ii formed pad of this association. Oenothera humifiisa, 

 Euphorbia polygon if alia, Cenchnis tribuloides nuicroeephahus, Mol- 

 lugo verticiiiata, and other species which are most, at home in the 

 second bell sometimes stray to the outermost dunes. Depauperate 

 specimens of Myriea caroliiwtisis, only 3 decimeters (1 foot) or so 



J , t , ■ ■ t l- * 



Fig. ttl. Ivd imbricata on the dunes near < 'ape Henry, Va. 



high, sometimes occur here, as do occasional specimens of other 

 woody plants. lint these are to be regarded as, in a way, accidental 

 cases. 



MIDDLE (OI'EN) DUNES. 



Myriea assoeiatwn.— Here CaMe edenlula and Salsola kali fre- 

 quently occur, bin are not characteristic, rniolajianieulata and Ira 

 imbricata are absent., while, on the other hand, Ammophila armaria 

 fin&Panicum amarum minus are almost- or quite as much at homeason 

 the outermost dunes (fig. 62). In sheltered, flat places Ammophila 

 sometimes makes a comparatively dense, almost, meadow-like growth, 

 often associated with scattered depauperate shru bs— My rica caroli- 

 nensis, Quereus virginiana maritima, Rhus copallina (fig. 63). The 

 higher sand hills are often occupied by dense thickets of Myriea 



'Apparently an undescribed species, nearest the European X. italicum Murr. 



