18 PLANTS OF MAST-HEAK ISLAND. 



wards the formation of its manj^ islands. Mr. Charles 

 Hedley*, to whom we are indebted for considerable inform- 

 ation respecting Mast- Head Island, considers that it was 

 formed by the action of tides in the shallow waters. Drifts 

 of sand apparently develop, and through the interaction 

 of lime and water a core of rock is formed. Depositions 

 of matters are constantly added to its bulk, until we have 

 an island centre, and a lagoon, suitable for the growth 

 around of a wonderful world of coral organisms. The 

 island sand is soon enriched by the excretse of birds and 

 it forms a fit soil for the development of a wealth of 

 vegetable life. The great Greeks who worshipped art 

 conceived their goddess of love and beauty as rising from 

 the pure waters of ocean. And is not much of the glamour 

 and fascination experienced by visitors to one of these 

 coral islands on the Barrier Reef due to the fact that these 

 little paradises are sea-born — the work of the waves and 

 of ocean organisms ? 



Mast- Head Island is situated just outside the Tropic 

 of Capricorn, 31 miles from the mainland near Port Curtis, 

 and is but 160 acres in extent. f The outstanding feature 

 of its botany is the luxuriance attained, although com- 

 paratively few forms participate. Aj)parently the 

 potentialities of the environment, so far as Phanerogams 

 are concerned, are utilised to almost the same extent as 

 though treble the number of forms were competing for 

 sustenance. We have here a striking illustration of the 

 advantages to an individual species of an island habitat 

 where the struggle for existence is less keen than on the 

 mainland. Of the first plants established, a very large 

 proportion of offspring must have survived. We may 

 expect in such insular floras opportunities for the develop- 

 ment of variations which the curtailing influences of Natural 

 Selection might stamp out in less congenial habitats. The 

 position is somewhat analogous to some of Luther Bur- 

 bank's experiments, where, in order to get all possible varia- 

 tions, the fullest scope is given to every seed of the selected 

 plant. Both in botany and zoolog}" we find island varieties 

 of mainland species. A surprising number of specimens 



*Proc. Lin. Soc, N.S.W., 1906, Vol. XXXI., part -3 

 fCommonwealth Year Book, 1912, p. 60. 



