BY A. A. HAMILTON. 175 



driven out or a change in the conditions again weakens the Sali- 

 cornia, and permits its opponent to reassert a temporary suprem- 

 acy. A typical example of this intrusion was noted at Hen and 

 Chickens Bay, where the Salicornia carpet surrounding the Man- 

 groves is exceptionally compact. Near the boundary of St. 

 Luke's Park, a weak salient in the Salicornia has been occupied 

 by the Seablite, which has entered its carpet in a wedge-shaped 

 formation, whose apex has reached the Mangroves, completely bi- 

 secting the Salicornia sward. The boundary of the joint formations 

 on the northern side runs along the fence of the Rifle Butts with 

 a well-defined line of demarcation, the intrusive Seablite, pallid, 

 and taller than its rival, attracting the attention of the observer 

 from the marsh bank. At Homebush Bay a dyke has been 

 thrown up along the bank of the tidal channel running through 

 the centre of the marsh to protect the plain from floods. The 

 Seablite has taken advantage of the resultant, alteration in the 

 habitat and obtained possession of the station on the banks of 

 the tidal channel intermediate between the dyke and the Man- 

 groves, fringing them with a narrow border (Plate xxii., fig. 11) . 

 In the artificial habitat created by the stoppage of the tide flow, 

 the Seablite has its opponent at a disadvantage, as the Salicornia 

 is unable, under the supervening dry conditions, to construct a 

 ••arpet, its formation breaking up into small patches or indi- 

 vidual tufts. The narrow margin of superiority held by the 

 Salicornia over the Seablite is well demonstrated on the broad 

 expanse of plain affected, where neither species is capable of 

 maintaining a massed carpet, both breaking up into small patches 

 or individual tufts and frequently intermingling (Plate xxiii., fig. 

 13), the Salicornia by virtue of its perennial habit eventually 

 supplying the major portion of the plain vegetation. On a sec- 

 tion of the marsh at a point opposite the Concord West railway 

 station, the plain is traversed by two almost parallel branches 

 of the central tidal channel, which extend for a considerable dis- 

 tance in the direction of the marsh bank enclosing a strip some 

 30ft. wide. The banks of the shallow waterways are lined 

 with Mangroves which display a graduated reduction in develop- 

 ment as the channels merge into the plain, the attenuated bushes 

 at the extremities, where the tide flow ceases, limiting their foliage 

 to a few scattered leaves (Plate xxii., fig. 12) . This natural 

 avenue lends a unique feature to the landscape, the enclosed 

 space, which is slightly raised above the level of the plain, cany- 



