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These plants have evolved unique structures—swollen stems, hollow thorns, or even bulbous roots—that act as living homes for entire ant colonies. Imagine the inside of a cactus or tree trunk ...

Scientists have difficulty determining the age of these behemoths, though — they stop forming rings and often have large, hollow interiors ... spaces between fused stems disposed in a closed ...

There have been cases of children using the hollow stems as whistles, leading to death. Dead stems can contain poison for up to three years. While the amount of poison can vary between plants ...