BY MARJORIE I. COLLINS. 379 



Avieennia officinalis is recorded as being the only woody plant in Western 

 Australian mangrove formation south of the Tropic. 



Ostenfeld refers to the mingling of the succulent halopyte Suaeda with 

 mangrove at its higher levels. Paulsen's work on Western Australian Cheno- 

 podiaceae points to this being a new species, viz., Suaeda australis (1918, p. 65). 

 The absence of other plants amongst the mangrove is attributed to the great 

 force of the tides which reach a velocity of ten to twelve knots in places 

 (Ostenfeld, 1918, p. 8). 



In the salt pan formation, Ostenfeld describes the plant covering as being 

 chiefly cushion forming Chenopodiaceae, species of Arthrocnermnn, also <S'a/»- 

 cornia aiistralis and Samolus jimceus R. Br., etc. (Ostenfeld, 1918, PI. 1, 2.) 



In a recent paper on saltmareh vegetation in the Port Jackson district, 

 N.S.W., Hamilton (1919, p. 470) refers to three plant formations in the local 

 estuarine flora. These are : — 



1. The Tide-flooded Zone, witli Aviaeimia officinalis and Salicornia aus- 

 tralis as dominants. 



2. The Dry Salt Plaix, with sparse vegetation and scattered detritus 

 mounds. 



3. The Fluvial Zone, separated from the former by a band of Casuarina 

 glauca Sieb. (the Swamp Oak), and marking the encroachment of fresh 

 water conditions upon brackish and saline. 



Botanical Features of a typical tidal Marsh near Sydney. 



The vegetation of a typical tidal marsh in the neighbourhood of Sydney, 

 is made up of two plant formations : — 



1. An outer Tidal Woodland or Mangrove Formation. (Pl. xxvi.. 

 Photo 1). 



2. An inner Saltjiarsh Formation. 



In mangrove formation, there can Ijc recognised Init one plant association, 

 comprising Avieennia officinalis and Aegiceras majiis, while in saltmarsh for- 

 mation there are generally two distinct associations, the outer in which Salicornia 

 aitstralis and Suaeda australis* are usually co-dominants, and an inner, which 

 marks the landward boundary of the marsh, is an almost dosed association of 

 the rush Jmicus maritimus Lam. 



Pioneer Pliase of a ti/pical tidal Marsh. 



In the pioneer phase, the typical tidal marshes around Sydney are colonised 

 by viviparous seedlings of Avieennia officinalis drifted up by the tides. The 

 seedlings are provided with a pair of large fleshy cotyledons, surmounting a 

 short, blunt hypoeotyl (Text-flgs. 2-'l). They establish themselves readily, or 

 are bound down by mats of the Alga Cladophora until the first roots have made 

 their appearance. Avieennia grows on the outermost limits of the formation. 

 It reaches a height of from fifteen to thirty feet and presents a striking ap- 

 pearance owing to the varying angles at which the trunks are bent to the fore- 

 shore (PI. xxvii., Plioto 2) and to the countless a.sparagoid ])neumatophores 

 which project vertically out of the mud (PI. xxvi.. Photo 3). These pneumato- 



* Ove Paulsen's work on Chenopodiaceae (1918, pp. 55-66) indicates that the species of 

 Suaeda in Australia hitherto known as S. maritiina should he known as 5. australis R.Br. 



