PRESIDENTIAL ADDRESS. 



40 



The zosteretum flourishes on mud banks, where there is a 

 considerable admixture of sand. At low spring-tide this 

 vegetation is laid bare, thence it continues downwards for 



Fig. 13. Blade-leaves of Zostera nana, principal plant of the zosteretum. 



several feet. Before the advent of civilisation disturbed 

 the balance of nature, the dugong (Halicore dugong) would 



D— May 5, 1915. 



