359 
Ridley . — On the Dispersal of Seeds by Wind . 
open spaces in woods. In cultivated land are a number of introduced 
weeds, Compositae chiefly, which have plumed fruit; but many of these 
migrate more rapidly by attaching themselves to clothing (e. g. Ageratum 
conyzoides ) than by the action of the wind. This is very marked where 
new country is being opened up by paths through forests, where these 
adhesive plumed Composites appear in a new clearing connected by a path 
with an old one long before the non-adhesive ones do. Indeed, of the 
Composite weeds common in this region the greater number are plumeless. 
On sandy or muddy shores, where the country is treeless or nearly 
so, we have Pluchea Indica , and also Spinifex , the heads of which are rolled 
along the sandy shores. The Lalang grass Imperata cylindrica has plumed 
seeds which become detached by the wind and drift away ; but the plant is 
only two or three feet tall usually, and I found in a fairly strong wind only 
flew on the level for about 1 6 yards. From hill-tops and such places it 
might fly further, but it seems never to migrate over a forest belt of about 
30 yards thickness. If a clearing is made in forest Lalang does not 
appear unless through a wide open path, or when it is carried by man, 
Quite a narrow band of thick wood will often stop its movements com- 
pletely. 
Of jungle trees with plumed seed or fruit we have very few, and these 
are usually more abundant in open country and edges of woods : Vernonia 
arborea , a fairly tall tree, abundant in open cleared land but not at all 
a forest tree, Vallaris , and two or three Alstonias. The seeds of Alstonia 
scolaris , a very tall tree, I have seen drifting at the distance of a hundred 
yards and more from the parent tree. They perhaps drift much further 
even in forest, but it is very difficult to follow them in dense woods. 
Clematis and Naravelia have plumed fruit. They are climbers on the 
edges of woods generally, and are not common. Of the Apocynaceae, 
besides the Alstonia and Vallaris mentioned above, there are a number 
of plume-seeded genera and species, of which a few inhabit the forests, 
climbing to the tops of the trees ; such are Urceola and Parameria. The 
shrubs Stropha?ithus and small climbers Parsonsia , Wrightia , &c., only 
occur in open country or edges of woods. 
Parameria poly near a is a big forest climber ascending to 60 or 70 
feet on the trees. It fruits heavily. The seeds drift in a good wind 
for 60 to 100 yards, slowly descending. If they fall on open ground 
such as a path or grass they drift along it still further. From a climber on 
a tree 60 feet tall in the Botanic Gardens, I find the furthest seed drop- 
ping at forty yards in a fair wind and drifting along the path for another 
60 yards. Plants occur in the jungle at a distance of about 108 yards 
from this big plant, and are doubtless derived from it. As these plants 
fruit when comparatively young, and frequently occur along the edges 
of woods and such spots where the fallen seeds can drift along more open 
