Lithops

Lithops are self-sterile, so that seed will only be produced if the plant is pollinated from another specimen from a different clone or group. Yellow flowers will not fertilize white and vice-versa. There is not the same range of flower colour as shown by the conophytums; lithops’ flowers are either white or yellow.

And the succulents house, which is kept a cool 60 degrees during the day and 50 to 55 degrees at night, holds aloes and lithops (which look like small stones), just beginning to bloom.

Lithops (‘Lithops’ singular) are easily one of Earth's weirdest plants making them highly popular with succulent lovers. They're also infamous for being easy to kill. In fact, I bet we'd be hard pressed to find someone who has never killed a Lithops unless they've just never had one, and that doesn't count.