15 APRIL 1938, Page 17

Plant Poisons

Many years ago one of the greatest of our biologists, now the sole survivor of the Ross expedition, found the Chinese poisoning fish with derris root. He did a deal of work in investigating the essence of the plant and methods of extraction ; and today derris is among the most important of insecticides in Europe. It will destroy certain weevils that have almost completely defeated other poisons. Fish are poisoned with equal success and harmlessness to men by extractions from native plants on the river Amazon. It may be worth while suggesting to some traveller on the British ships that still steam up the river and bring back nuts, rubber and timber that he should investigate the nature of these plants, as Professor Durham investigated derris. It may well be that they, too, contain a valuable principle by which cultivators in other continents might profit. Another method of killing fish that is practised on the Amazon, as even the casual traveller may observe, is by the agency of that antique weapon, the bow and arrow ; but it is being surrendered, I regret to say, in favour of the explosive bomb, which was much used for this purpose both by our soldiers and the French in the

Great War. * * * *