THE BOTANY OF CHRISTMAS ISLAND. 269 



Plumed seed and fruits. 



These are chiefly of plants belonging to the orders Apocy- 

 naceae, Asclepiadeae, Compositae, with a few Gesneraceae, and 

 grasses. The seed or fruit are disseminated by wind, and it 

 might be thought that these would readily be conveyed to 

 Oceanic Islands, as are the dust seed plants. This is not the 

 case. They are comparatively scarce, and curiously most of the 

 Compositae of Oceanic Islands are the ones which have plume- 

 less fruits, introduced weeds excepted. Only 3 plants . with 

 distinctly plumed fruits or seeds are known from Christmas 

 Island, of these one Ageratum conyzoides is certainly a weed. 

 The others are Blumea spectabilis and Hoy a Aldrichi. The 

 former is a hill forest plant of the Malay region, the latter an 

 endemic species allied to Javanese species. 



Winged fruit and seeds. 



These are still rarer than the plumed seeds, and of the 

 very few that are to be met with in Oceanic Islands, it may be 

 doubted very much whether their wings have played a large if 

 any part in their dissemination. The Dipterocarpoe for instance 

 are quite absent from Oceanic Islands. Gyrocarpus which 

 occurs in Christmas Islands and other Islands a sea shore plant 

 is certainly disseminated by its wings, but I suspect it reaches 

 the islands by sea. I cannot conceive of the winged fruits of 

 Berria being drifted by the severest gale for two hundred 

 miles, as it is really hardly adapted for flying more than about 

 40 yards, yet it occurs on Christmas Island. The fruit is 

 a winged capsule which splits when ripe and releases its 

 pubescent seed, so that really ripe fruit if blown out to sea 

 in a gale of wind, would almost certainly break up ere it had 

 gone far and the seed would fall into the sea. 



Dust seed. 



The very fine dust like seed of orchids, and Balano- 

 phara and the spores .of ferns, Lycopods and cellular 



R. A. Soc, No. 45, 1905 



