C. H. Ostenfeld: Contributions to West Australian Botany. II. 7 



1. The 3fangrove Formation. 



The West-Australian mangrove extends much farther south 

 than the tropic of Capricorn. L. Diels 1 mentions it as far south 

 as Bunbury (Lat. 33V 2 ° S.), near the south western corner of the 

 continent; but south of the tropic it is very monotonous, the 

 Grey Mangrove (Avicennia officinalis) being its only wood-plant. 

 This shrub, or small tree, is also the main component of the tro- 

 pical mangrove of W. A., but it is not the only tree. At Point 

 Samson (near Cossack) the low Ceriops Candolleana was com- 

 mon, and at Port Hedland the taller Rhizophora mucronata 

 formed extensive growths along the inner part of the estuary, 

 while Avicennia ruled at the outer part. At Derby, at the head 

 of King Sound, where the large Fitzroy River has its outlet, 

 the mangrove near the jetty had Avicennia as dominating 

 species (Plate I, Fig. 1). But against its dull dark-green and grey 

 foliage the bright and shining green of another low tree, which 

 occurred only in scattered individuals, made a striking contrast. 

 This was Excoecaria agallocha (var. ovalis), a plant widely distri- 

 buted in the coast regions of the Old Worlds tropics. 



In the higher lying parts of the mangrove at Derby a suc- 

 culent undershrub formed a green cover under the shrubs ; it was 

 a form of Suæda. As it was without flowers and fruits, having 

 shed the fertile branches, I could not refer it to its proper place, 

 and am much indebted to Mr. J. H. Maiden for his help in this 

 matter. He has named it S. maritima; but it differs greatly from 

 the plant as I know it from the shores of Europe. Here, it is a 

 perennial plant and its lower parts are woody. I think it ought 

 to be taken as a species distinct from our European plant. This 

 is also the opinion of dr. Ove Paulsen who has examined my 

 Chenopodiaceæ; he names it S. australis (R. Br.) Moq. 



The northern part of West Australia is known for its very 

 pronounced tides. It is reported that the tide at Derby reaches 

 to 10 — 15 meters and at Broome and Port Hedland not much 

 less. The steamer arriving at high water off the head of a jetty, 

 must remain there until next high water; and at low water time 

 the water around it has quite disappeared, and it stands on the 

 sea bottom supported by the logs of the jetty (see Fig 3). Such 

 a marked difference between high and low water makes a strange 

 impression on the visitor. He sees at high water the mangroves 

 growing in water which reaches the green foliage of their crowns, 



1 L. Diels: Die Pflanzenwelt von West-Australien südlich des Wende- 

 kreises. 1906, p. 207. 



