"Plenty of them," answered the scientist. "There are over a hundred plants which give off smells or vapors which are injurious either to man or animals. Some are used by savages for arrow poisons, others for fish poisons, and some we use for medicinal drugs. Dixon records a 'gas-tree' in Africa, the essential oil of which contains chlorine and the smell of which is like the poison-gas used in the World War. And poison-ivy, in the United States, will poison some people even if they only pass close to it."
"Jes' how does a tree make a smell, Mister Ol' Doc?" queried Mark.
"That's hard to explain to you," answered the scientist, turning to the negro. "But every plant has some kind of a smell, that is, all of them have essential oils which volatilize in the air. Some, like the bay, have these oil-sacs in the leaves, some, like cinnamon, in the bark, and so on. The smell of flowers comes the same way."
"An' there is mo' kinds of debbil-trees 'an them on Terror Cove?"
"Plenty more kinds," was the answer, "though few of them are as deadly. These are famous. Lord Nelson, when a young man here in Barbados, was made very ill by drinking from a pool into which some branches of the manchineel had been thrown. In fact, he never really got over it."
"How about me, Doctor?" enquired Stuart. His face was flushing and its was evident that the semi-paralysis of the first infection was passing into a fever stage.
"It all depends whether you ate any of the fruit or not," the doctor answered. "If you didn't, you're safe. But you seem to have spent an hour in that poison-tree grove, and that gives the 'devil-trees,' as Mark calls them, plenty of time to get in their deadly work. You'll come out of it, all right, but you'll have to fight for it!"