TREE FORMATION. 271 



plants of Yucca gloriosa, with fleshy rootstocks often exposed by the 

 shifting of the sands, are frequent on the lesser dunes. The sinjjjle 

 specimen of Yucca aloifolia observed was over 2 meters high, with 

 stem branched several times above the ground. Botli species have 

 exceedingly hard and sharp spinous leaf tips. On some of the liiglier 

 dunes depauperate plants of the shrubby il/?/rica caroVniensiii^ mostly 

 onl}^ 3 to 6 decimeters high, associate with the Uniola. Of secondary 

 importance in this association are two perennial grasses, Paniruyyi 

 amarurn minus and Spartina patens (juncea); as well as a probably 

 biennial thistle, Carduus spinosissimus (Cnicus horridulus) ; and 

 several other herbs, among them the white-sericeous Oeuothera humi- 

 fusa and Croton maritimus. 



EVERGREEN TREE AND SHRUB FORMATIONS. 



TREE FORMATION. 



Scattered over the island, but preferring the higher dunes which 

 occupy its inner side, are small groves of live oak, Quercus virgin tana 

 (Q. virens), either in pure association or mixed with some other trees. 

 The oaks are usually 6 to 9 meters high and 3 (rarely 7^) decimeters 

 in diameter. Those on the northern edges of the groves have trunks 

 strongly inclined toward the south, and, as a consequence of the deiUi- 

 dation of the branches on the windward side, the whole crown of 

 foliage lies to leeward of the axis. One could not desire a better 

 indication of the prevailing direction of strong winds in the region.^ 

 The branches, gnarled and twisted, are clad with numerous lichens, 

 chiefly Usnea barbata, and with occasional small wisps of Spanish 

 moss {Tillandsia usneoides), which evidently maintains but a precari- 

 ous foothold on the trees of this wind-exposed island. 



Altogether the aspect of the groves is rather weird and somber. 

 Often associated with the oaks are small trees of Mijrica cerifera, Zan- 

 ihoxyluin clava-Jierculis and Ilex vomitoria, all of about the same maxi- 

 mum size (G meters high and 2 decimeters in diameter), and occasionally 

 Ju7iiperus virgimana, which rarelj" attains a height of *J meters and a 

 diameter of 3 decimeters. Lianas are sparingly represented by S)n ila.v 

 hona-nox, Vitis aestivalis, and Rhus radicans, all three species some- 

 times attaining considerable size and climbing to the tree tops. The last 

 is, however, usuall}^ of the creeping form, with the main stem under- 

 ground. The herbaceous members of this association are, in the 

 smaller groves, chiefly plants characteristic of the open strand, Cldoris 



'All the specimens of live oak seen were apparently of considerable a2re. Seed- 

 lings were few or none, and no acorns were observed. It is probable that instead 

 of increasing, the oak is here holding its ground with difficulty. So highly are the 

 trees valued as wind-breaks by the inhabitants that none are felled, all fuel being 

 brought from the mainland. The rounded shrubby form of this plant, common 

 elsewhere on the coast, was not observed on Ocracoke. 



