288 



A. A. HAMILTON. 



the frequently occurring lagoon or the general contour level 

 is reached. The northern section of the shoreline consists of 

 Narrabeen Shale superimposed on the reef. Throughout 

 this area in which the soil is comparatively rich, the indi- 

 genous vegetation has been removed, and the ground 

 dedicated to a pasture of "Couch-grass" Cynodon dactylon 

 Rich., which creeps out to the verge of the ocean headland 

 or the dune embankment. 



South of Deewhy the shale is replaced on the headland 

 by the coastal sandstone. The broken escarpment, and 

 the shelving parapet immediately above, are sparsely clad 

 or frequently quite bare, a shallow layer of soil finding a 

 lodgment here and there in depressions of the rock benches, 

 or filling pockets and crevices in the reef, and supporting 

 a scanty, storm-bitten vegetation. On the rocky hillside 

 the plants are chiefly shrubby, most of the herbaceous 

 species, with the exception of Glumiferce, retreating inland 

 or descending to the dune. The vegetation on the dune 

 front is largely herbaceous, though several shrubby species 

 reach the plateau of the embankment. The bulk of the 

 ligneous vegetation does not, however, venture within 

 range of the periodic storm visitation, which denudes the 

 frontal embankment and deposits its spoil on the rearward 

 slopes. The frontal dune slopes are scantily furnished, 

 and competition between the scattered plant colonies is 

 consequently limited, permitting, in many instances, fairly 

 large areas of a practically pure specific formation. 

 Occasionally, however, especially among the rhizomatic 

 species, two or more struggle for supremacy, and frequently 

 the individual competition within the colony is exception- 

 ally severe. 



The gregarious sylvatic species on the rearward slopes, 

 have generally adopted an open forest formation, in which 

 a thick undergrowth finds protection, a notable exception 



