494 ECOLOGICAL STUDY OF SALTMARSH VEGETATION. 



Several Tea-trees, Melaleucas, all of which .are confined to 

 Australia, constitute the major portion of the ligneus vegetation 

 in the Casuarina forest (Plate xxvi., fig. 19) . They have 

 xerophytic leaves ranging from the prickly foliage of M. nodosa 

 Sm., the less harsh and smaller cylindrical leaves of M . ericifolia 

 Sm., the broader and frequently twisted leaf blade of M. styphe- 

 lioides Sm., to the somewhat flattened elongated leaves of M. 

 linariifolia Sm. M. ericifolia, a shrub of 3—6 feet, less plastic 

 than its congeners, is confined to a moist soil frequently extend- 

 ing its colony on to the tide-flooded mud-banks projecting into 

 the stream and covering them with a dense exclusive growth. 

 Though tolerant of periodical tide-flooding, this species is not 

 strictly halophytic, as it forms comparatively large colonies in 

 the fluvial mud at the head of the marsh. M. styphelioides, and 

 M. linariifolia, do not reach their optimum growth in the 

 Casuarina forest, as they are dominated by the latter which 

 outgrows them, but on the Wianamatta Shale flats in the Banks- 

 town-Cabramatta districts these Tea-trees attain an arboreal 

 growth equal to that of the Casuarina. Both Melaleucas are 

 occasional on the local sandstone in swampy places but neither 

 can maintain more than a shrubby growth on the dry sandstone 

 hillsides. M. nodosa attains its individual optimum in the 

 Casuarina forest where the canopy formed by its taller associate 

 compels it to ascend to obtain light, but its maximum communal 

 growth is reached on the shale flats where, though inferior in 

 height, it spreads laterally, covering areas several acres in extent 

 with an exclusive thicket. It is also capable of maintaining a 

 vigorous but less compact colony on the Hawkesbury Series, 

 both on the rocky ocean escarpment and the landward sandhills 

 M. ericifolia is unable to accompany its swamp associates to 

 the dry shale flats but a reddish-purple flowered variety, var. 

 erubescens Benth., mingles with the other Melaleucas in the Clyde- 

 Auburn district at a distance from the marsh. Of the Tea-trees 

 noted, mature seeds sank within 12 hours. 



The Blackthorn, Bursaria spinosa Cav., a spiny shrub endemic 

 within the Commonwealth, has a sparse representation in the 

 Casuarina forest and occurs in company Avith Melaleuca nodosa 

 on the shale flats, where it congregates in large colonies. These 

 shrubs are also frequently associated on the sandstone hills. 

 The Bursaria is exceptionally rigid in its habit of growth which 

 varies but slightly under widely differing conditions of soil and 



