490 
WEED-PESTS. 
t Ih many agricultural journals one may read of pestilential 
plants accidentally or intentionally introduced by man from other 
parts of the world, which grow to such an extent that they 
become a nuisance, and are often very difficult to eradicate. 
In the “ Journal d’ Agriculture Tropic ale, Paris (No. 35, May 31, 
1904), M. des Grottes writes: “ That the introduction of new 
‘‘plants into our Colonies requires much circumspection and 
careful^ preliminary study, for whilst some are useful others are 
noxious.” Among the noxious plants he' places the Guava. 
Other gardeners have the same cautious fear I find of introducing 
a plant to their country which may possibly become a noxious 
weed. It is, however, a fact that plants with the worst possible 
reputation as weeds, often under apparently exactly the same 
circumstances of soil and climate, refuse to take to the country 
at all, and are quite harmless. A species of Oxalis is a pest 
in the tea gardens of Ceylon. It grows by underground tubers, 
and is difficult or almost impossible to eradicate. In the Malay 
Penmsula, however, it hardly manages to exist, except on such 
spots as Penang Hill, where it thrives but is quite easily disposed 
of. Argemone Mexicana, an ornamental poppy, has established 
itself as a pest in many parts of the world, and due caution was 
exercised in introducing it as a bedding plant into Singapore. 
It grew, flowered, seeded, apparently well the first year and 
utterly vanished the second year. 
In the Antilles M. dfs Grottes declares that the Guava has 
run wild, is terrible pr iific, and the roots are very hard, sink 
deep into the soil, and are very troublesome to eradicate. The 
seeds are dispersed by cattle and pigs and also by birds. In 
the Malay Peninsula "the Guava is very widely cultivated, and 
occasionally seedlings spring- up here and there m waste ground, 
but it is very far from establishing itself as a pest. It reproduces 
very slowly in a half-wild state. The reason for this is probably 
that civet cats and bats eat the fruit before it is ripe, so that 
no seedlings are produced. I have but rarely seen a ripe fruit 
on a half-wild seedling Guava here, though where the fruit 
is protected to some extent in gardens it fruits very well. 
Among plants accidentally introduced into the Malay Peninsula 
which have become more or less of a nuisance are the sensitive 
plant Mimosa pudica, the large shrub M. sepiaria, the common 
Lautana, Lautana mixta, lalang, Imperata cylindrica , Limnocharis 
plumieri, an ornamental plant cultivated by the Chinese for pig- 
food which has wandered into ditches and rice-fields, and some 
other weeds. 
The most curious thing about many of these weeds is the way 
that at first they seem to grow with great rapidity and prove a 
general nuisance, becoming extremely abundant, and then seem 
almost as fast to die away and become scarce, or at all events not 
more common than any other plant. 
