406 ECOLOGICAL STUDY OP SALTMABSH VEGETATION. 



marsh is the joint production of the mangrove forest and the 

 Salicomia meadow, the latter, with its monotonous stretch of dull- 

 green, stunted herbage, framing the mangroves with a sombre 

 border. The lack of diversity is due to the harsh conditions 

 obtaining in this exclusive station, which have limited the vege- 

 tation to a few species. The portion of the plain lying between 

 the Salicornia and the marginal formations is broken by scat- 

 tered detritus hummocks and ridges, and intei'seeted by water 

 channels and occasional pools which harbour a weak scanty 

 herbage, the remnants of several communities. Large stretches 

 of this inhospitable station are bare of vegetation, except where 

 clothed with a filamentous algal deposit, the surface, in the lengthy 

 intervals between tidal visitations, becoming sun-cracked and 

 flaked (Plate xxiii.,fig. 13) or, in places, encrusted with a glisten- 

 ing coat of salt (Plate xxiii., fig. 14) . The marsh plain is 

 frequently fringed by reed formations which extend along its 

 margin in elongated bands (Plate xvii., fig. 1), their tall, closely- 

 ranked stems providing a pleasing alternative to the degenerate 

 herbage of the salt plain. 



In several local marshes the Swamp Oak occupies a position 

 on the plain boundary, lining its banks in a belted avenue, or 

 spreading into a forest on the fluvial mud flats at the head of 

 the marsh. This quaint tree lends a picturesque character to 

 the scenery, with its ascending tufts of ashen grey branchlets, 

 encircled at their joints by toothed whorls of rudimentary leaves 

 and the rough corrugated bark usually draped with varicoloured 

 lichens. Tea-trees, Melaleuca spp., form the bulk of the shrubby 

 undergrowth in the Casuarina forest (Plate xxvi., fig. 19) their 

 heath-like foliage blending harmoniously with the narrow cylin- 

 drical branchlets of their taller associate. The loose, smooth, 

 papery bark of the Tea-trees presents a marked contrast to the 

 wrinkled compact cortex of the Swamp Oak. 



The outlying formations are less regular in outline and volume 

 than the central groups. The scarcity of mosses, noted by 

 ecologists as exceptionally halophobus, was observed in the local 

 marshes. The lichen flora on the contrary is well represented, 

 chiefly on the Casuarina trunks. Though occasional on the 

 mangroves exposed to the light at the fringe of the forest, the 

 lichens are unable to penetrate its heavily canopied interior. 

 Rosette-forming species are rare in the tide-flooded zone and on 

 the salt plain, though the detritus heaps occasionally harbour the 



