388 NOTES ON THE FLORA OP THE BLUE MOUNTAINS, 



the debris at the base of the uppermost ledges of the escarpment 

 to within a few feet of the level of the tableland, the process 

 being repeated on the other side of the mountains via the Valley 

 of the Grose. 



King's Tableland, Wentworth Falls, forms a natural bariier 

 east and west, which either checks or entirely prevents the 

 ascent or descent of many species. On this bleak, wind-swept, 

 soil-denuded plateau, which is typical of much of the area west- 

 ward and upward, a xerophytic flora is in undisputed possession; 

 and many of the plants from the coast and foothills, which have 

 reached the elevation at Lawson, find the ascent of this sterile 

 ridge a feat beyond the limit of their endurance, and are content 

 to remain in the shelter of its eastern slopes. On the other 

 hand, most of the dry-ridge xerophytes descending from the 

 higher altitudes make their last stand on this elongated spur, 

 finding on it the lowest elevation to which they can safely de- 

 scend. A percentage of the swamp-xerophytes, chiefly Glumi- 

 ferse, persists to a much lower elevation. 'Ihis objection, on the 

 part of the dry-ridge xerophyte, to surroundings which would be 

 considered ideal by many plants, is exemplified in the case of 

 Eriostemon obovalis A. Cunn., which grows on the baldest and 

 most exposed hilltops out to the clifJ'-edge. The fruits of this 

 species are of the explosive type, and, when ripe, the polished 

 and somewhat rounded seeds are expelled with considerable 

 force, many of them rolling over the cliffs into the rich detritus 

 of the moist, sheltered gully below. The seeds, howe\er, resist 

 the softening influence of the unfamiliar environment, and 

 decline to germinate. The winged seeds of Casuarina 7iana 

 8ieb., which are carried by the wind into positions favoured by 

 most plants, provide another instance of the characteristic in- 

 ability of the dry-ridge xerophyte to reproduce itself in unacus- 

 tomed surroundings, which will at once recur to botanists familiar 

 with the Blue Mountain flora. Apparently an exception is pro- 

 vided by Boronia anemonifolia A. Cunn., which, when growing 

 on the ridges, is an insignificant, scabrous, twiggy shrub, a few 

 inches high, but gradually improves in size and appearance as it 

 descends into more hospitable quarters, and, finally, becomes an 



