BY H. A, LONGMAN. 19" 



from island habitats appear in records with no specific 

 name attached or are noted as varieties. This is par- 

 ticularly true of the Challenger Volume by Hemsley, on 

 Insular Floras. In certain species a change in environ- 

 ment tends to increase variability, and this is surely true 

 of many plant immigrants on islands. 



The study of insular floras reveals successive stages in 

 plant colonisation. My list from Mast- Head numbers only 

 twenty- six species, two of which are but carpological and 

 represent unestablished forms. There may be, of course, 

 additional annual plants, not found during our visit.* 

 We may anticipate that a census taken some years hence 

 will show an increase, even though some species fail to 

 survive. The majoi^ty of the plants found are naturally 

 conspecific with those on the adjacent coastal districts. 

 AVith these the most interesting point is not a mere 

 enumeration of names, but an inquir}^ as to the method 

 of colonisation. Primary importance should be given 

 to ocean currents. I w^as fortunate in securing a pod of 

 Castanospermum australe, A. Cunn., the Moreton Bay 

 Chestnut, which had been washed high on the beach, and 

 which in the ordinary course of things might have taken 

 root and flourished. Our veteran botanist, Mr. F. M. 

 Bailey t, has noted a fruit of Parinarium laurinum, a Rosace- 

 ous tree found in Fiji and the Samoan Islands, which was 

 secured in a similar position on the island in 1907. In 

 this connection it is interesting to remember the experi- 

 ments of Darwdn, Guppy, Ch. Martins and others, demon- 

 strating that long immersion in sea water fails to rob many 

 seeds of their vitality. Casuarince and Pandani flourish 

 on coral sand debris, and are usually among the first comers 

 brought by ocean currents. Associated with them is the 

 common seashore grass, Thuarea sarmentosa, which has 

 valuable binding properties in loose sand. ]\Iast-Head 

 is circled by a gray-green belt of Casuarina equiseti folia. 

 The small cones of these trees sink in the water when green, 

 but when somewhat dr}^ they float and retain their vitality 

 for several days. Other plants in my list, the seeds of which 

 probably reached the island by ocean currents are SopJwra 



*Qld. Univ. Biol. Students' Trip, Sept., 1912. 

 tQkl. Asric. Journ., Feb., 1907, p. 76. 



