PRESIDENTIAL ADDRESS. 45 



nd Mgiceras majus. The latter grows as a bush, with 

 sweet-smelling white flowers, on the inland border of the 

 mangrove swamp. Though Avicennia has here outstripped 

 its tropical associates, Rhizophora, Bruguiera, Ceriops and 

 Acanthus, yet it is well within its boundaries, for it con- 

 tinues south as far as Wilson's Promontory. In New 

 Zealand it reaches Tauranga, and in West Australia it 

 extends to Bunbury. 1 These limits doubtless correspond to 

 isothermal zones. Even near Sydney the foliage is some- 

 times touched by an occasional frost. 



The Avicennia is a slow-growing tree whose proper home 

 is the soft black mud on the banks of saltwater creeks, but 

 which sometimes grows on the sandy border of a zosteretum. 

 It requires shelter and ventures on no beach unless land 

 locked from the sea. In the distance an Avicennia forest, 

 rising in domes about thirty feet high, has a resemblance 

 to an olive grove. The short trunk branches into crooked 

 boughs, well clothed with grey-green leaves, and casting 

 a dense shade. As the wind stirs the foliage their pale 

 undersides paint ashy ripples across the forest. At high 

 tide the leaves dip in the sea (Plate I, fig. 1), while low 

 tide exposes the pneumatophores or "cobbler's pegs" as 

 they are called popularly. These project densely from the 

 underlying radial roots to about eight inches above ground 

 (Plate I, fig. 2). 2 



So safe a perch above the suffocating mud do these 

 asparagus-like rootlets afford that they are sometimes 

 loaded with oysters or bristle with barnacles, Balanus 

 trigonus. The trunks of the trees are not neglected as 

 residential sites, and are well plastered with oysters. An 

 Avicennia leaf, which though less than three inches long, 



1 Alexander, Nature, June, 1913, p. 399. 



2 For this and other photographs of beach scenery I am indebted to 

 the kindness and artistic skill of my friend Mr. A. R. McCulloch, who 

 also drew for me the two fish. 



