An alien orchid that reproduces by merging with other organisms, whose enzymes cause the transporter to combine Tuvok and Neelix into a single being in Tuvix.
The symbiogenetic orchid is an alien flower collected by Tuvok and Neelix on a botanical survey in the Voyager episode Tuvix, set in 2372.
When the two beam back to the ship with samples of the plant, only one person materialises: a composite of both men who takes the name Tuvix. The Doctor and Kes discover that the orchid reproduces by symbiogenesis, in which separate organisms merge to form a new one, and that its enzymes acted on the two patterns during transport. Test transports using the flowers reproduce the effect.
It takes weeks to find a way of reversing the process, by which time Tuvix has become a valued member of the crew who does not wish to die. Captain Janeway carries out the separation herself.