8 
Ridley .— The Distribution of Plants. 
Amarantaceae, and such like introduced accidentally. All plants thus 
imported by man and run wild I class as weeds. 
Weeds. 
Weeds are usually identified by their being confined in their habitats 
to cultivated ground, or roads, or paths, as such classes of habitats did not 
occur previously to the advent of man, and it is clear that plants now con¬ 
fined to such spots in any given country must have been introduced by man. 
Some plants, however, like Lochnera rosea , the West Indian periwinkle, 
grow exclusively on sea-sand; others, like Capsicum minimum , Linn., 
establish themselves on limestone cliffs, or, like the Wallflower, on ruined 
walls, &c. In such cases their original habitat and place of origin can only 
be adduced by their history, if known, and otherwise by their affinities with 
other species allied to them. 
All weeds must have been wild in some country, but may have been so 
long diffused over the surface of the globe that it is very difficult now to 
identify their original home. 
A certain number of species of plants are only known in cultivation ; of 
these some are derived from well-known wild forms, especially those of 
western Europe, whose history we know. In other cases we can only guess 
the origin by knowing where allied species are still actually to be met with 
in a wild state. 
The greater number of the Malay fruit trees are not known in a wild 
state anywhere. They must have been wild somewhere in the Malay area, 
as they nearly all belong to local genera, but are specifically distinct from 
any species occurring in a wild state. The cause of this is, I think, that in 
very early days when a native found any of these trees in a forest he went 
and regularly gathered the fruit, taking it to his village, where the seeds 
thrown away germinated and formed an orchard. Often too, if a Malay 
finds an abandoned fruit tree in ripe fruit he fells it to save the trouble of 
climbing it. By persistently taking the fruit he prevents the tree reproduc¬ 
ing itself by seed in its native haunts, so that the species eventually dies out. 
Or again, if he finds a number of these trees together, he will start a village 
round them and so bring them into cultivation. This, I believe, accounts for 
the absence in a wild state of the Durian (Durio zibethinus , Murr.), Mango- 
steen {Garcinia mangostana, Linn.), Rambutan {Nephelium lappaceum, Linn.), 
and Pulasan [Nephelium mutabile, Bl.), Betel-nut ( Areca catechu , Linn.), and 
many other species which have never, so far as I have been able to ascertain, 
been found in a wild state. 
We have two difficulties in tracing the migration of weeds ; one is that 
our earliest herbaria are of so modern a date that we have little clue as to 
when the weeds first appeared, and secondly that, when botanists did begin 
