358 Ridley . — On the Dispersal of Seeds by Wind. 
Winged-fru't Plants in Insular Floras. 
Plants whose seeds or fruits are dispersed by the aid of wings are very 
rare in oceanic islands, about 2 per cent, of the species ; and of these in some 
cases I am doubtful as to whether the plants reached the islands by the aid 
of the seed- wings. Notoriously absent are the Dipterocarpeae, wing-seeded 
Apocynaceae, and Bignoniaceae. 
In Christmas Island I found only one, viz. Gyrocarpus , a sea-shore tree 
with fruit resembling that of a Dipterocarpus , and Berrya with smaller 
winged fruit, but both may possibly have been sea-drifted. In Fernando 
de Noronha were none, except possibly a Bignonia , the seeds of which 
were perhaps winged, but were not seen. There are none in Cocos Island 
nor the Admiralty Islands. Casuarina equisetifolia , which possesses thin 
winged seeds, is certainly sea-borne, as its distribution is that of other sea- 
borne species, and it is exclusively a sea-sand plant, springing up along the edge 
of the sea-beaches. It occurs on many of the islands of the archipelago. 
Of capsular plants with winged seeds, which drift from the split 
capsules when ripe, there are a number of trees in the Malay Peninsula and 
a few climbers. They include Cratoxylon , Gordonia , Archytea , Ptero - 
spermnm , Ixonanthes , Triomma , Oroxylon , Dolichandrone , Duabanga , Nor- 
risia , and Dyer a ; and the climbers Alsomitra , Zanonia , Coptosapelta , Uncaria, 
Wigktia , Dioscorea , Stemona , Nepenthes, and Aristolochia . The trees are 
usually small ones, except Dyera , and none are lofty plants like Diptero- 
carpeae. The climbers, too, are not usually large. The seeds being 
usually small, it is difficult to find them when fallen, so as to estimate 
the distance to which they can fly ; but I judge from the appearance of 
seedlings near the trees that they fly but a few yards. Dyera has been 
described already. Uncaria seeds are so fine that they fly like dust-seeds 
when the pods open, and might be drifted in the wind to a very long 
distance. I do not know of any plant with winged seeds on oceanic 
islands. 
Plumed Seeds and Fruits. 
Fruits and seeds provided with silky plumes fly a good deal further 
than winged fruit, both in forest and still more so in open country. The 
flight of this class of fruit or seed is better known from observations in 
temperate countries, where the ground is more open and the fruit has 
a clear space to drift along ; consequently these are more abundant than 
they are in a forest region, and indeed are much more easy to observe. In 
the Malay Peninsula we have very few indigenous terrestrial herbs with 
plumed seeds or fruits. The only ones inhabiting forests which I know 
of are Gynura sarmentosa , which is usually a low climber, and Blumea 
spectabilis. The former inhabits swampy spots in dense woods, but does 
often occur on the edges and on banks ; the latter, a tall herb, on banks and 
