Immense forests overspread the humid plains of Sumatra. They are constituted in the main of numerous species of Fig-trees (_Ficoidæ_), whose abundant and persistent leaves form an obscure vault, impenetrable by the sun's "golden arrows." Above this leafy dome shoot the rigid trunks of trees of lofty stature. Of these, the most remarkable, perhaps, is the Ipo-antiar (_Antiaris toxicaria_), whose juice, after having undergone certain preparations, becomes one of the deadliest known poisons. It was for a long time unknown with what substance the Malays envenomed their arrows and their famous _kris_, or crease; nor was it until the beginning of the present century that the traveller Leschenault ascertained, not without difficulty, that it had for its basis the juice of a very tall tree, with decaying leaves, to which he gave the name of _Antiaris toxicaria_. This is the celebrated Upas, whose deadly properties were formerly exaggerated in so many wonderful fables. The poison is prepared in an earthen vessel, and mixed up with certain quantities of the seed of the pimento and the pepper tree, and the roots of various kinds of ginger. These are mixed together slowly, except the pimento-grains, which are precipitated one by one to the bottom of the vessel by means of a small stick. Each grain produces a slight fermentation, and rises to the surface. It is then extracted, to be plunged anew into the mixture, and this process is eight or nine times repeated; after which the mixture is complete. It appears that the Upas-antiar, taken internally, acts at first as a purgative, but afterwards its influence extends to the brain, and produces death with frightful tetanic convulsions. Introduced into the blood through a wound, it kills small animals in a few moments, and men in a few hours. [Illustration: 1. Nipa fruticans. 2. Sugar Palm (_Areca saccharifera_). 3. Ipo-Antiar (_Antiaris toxicaria_).] Marvel-loving writers formerly asserted that this deadly poison was employed in the execution of criminals, who, however, received a pardon if they contrived to reach a tree, and bring back a supply of its venom. Birds, it was said, dropped dead while flying over it--as was formerly told of the pestilential waters of the Dead Sea--and the whole country around was desolated by its noxious effluvia. But the fact is, the upas tree is merely a tree with poisonous secretions, and in no way affects the atmosphere of the locality where it lives.