io Ridley .— The Distribution of Plants. 
Malay Peninsula, but it may be interesting to point out that the greater 
part of the Compositae occurring here, twenty-six out of thirty-five species, 
and a large proportion of the Labiatae, Amarantaceae, and Grasses in the 
southern part of the peninsula have been undoubtedly introduced within 
a comparatively few years. Indeed, exclusive of the Bamboos, the forest 
region covering the greater part of the peninsula, where unaltered, contains 
only single species of Leptaspis , Lophathcrum , and Centotheca , with one or 
two species of Panicum and Isachne. 
The mountain Gunong Tahan, never visited by man until Mr. H. C. 
Robinson reached it in 1905, bore only a few Grasses, viz. one of these 
Panicums and a couple of rare Isachnes. A few indigenous Grasses grow 
on the tops of some of the other mountains and some on the sea-shores, but 
far the greater number are clearly recent introductions. The number of 
weeds in our area is still increasing, and is likely to continue so doing for 
very many years. 
Methods of introduction of weeds. 
Weeds are introduced into new countries by a variety of ways, and 
I give here some account of the chief ways in which they are introduced. 
Undoubtedly very many seeds of aVIens are brought accidentally or 
intentionally into countries where they fail to make good or establish 
themselves. A study of Dunn’s ‘ Alien Flora of Great Britain 5 illustrates 
this very well. 
Weeds introduced in pot-plants. 
A certain number of plants have been introduced casually in soil in 
pots of plants sent from other countries, and have been able to establish 
themselves in their new homes. Conspicuous among them are Pilea 
muscosa , Lindl. (Urticaceae), and Pepcromia exigua , Miq. (Piperaceae), 
South American plants now established in the East Indies, and Cardamine 
hirsuta , Linn., probably of European origin but now spread over large areas 
of temperate or sub-tropical lands, though it does not seem to thrive in 
the tropics. The only time it appeared in Singapore it grew on rubbish 
heaps in the gardens, where the soil of pots of plants, sent, I believe, from 
Kew, had been emptied out. It failed to establish itself. Drymaria 
cordata , Willd. (Caryophyllaceae), a plant of unknown origin, is spreading 
all over the tropics in the same way, though it seems to confine itself to the 
highlands, about 5.000 ft. alt., in hot and wet regions. It appeared 
abundantly in the roadsides and gardens of the Semangkok Pass, Selangor, 
4,000 ft. alt., in 1921, probably introduced with rose-trees from Java. 
Weeds introduced in cereal or other seeds. 
A very large number of plants have been introduced into alien 
