Lithops can be grown on a sunny windowsill, but even experts are respectful of their abhorrence of water out of season.
From the dallasnews.com
Significant numbers of orchids, water lilies, cacti, lithops, carnivorous plants and bromeliads are housed in the various zones.
From the en.wikipedia.org
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Any plant of the genus Lithops native to Africa having solitary yellow or white flowers and thick leaves that resemble stones
Lithops is a genus of succulent plants native to southern Africa. "Lithos" means "stone" and "-ops" means "face" in Ancient Greek; therefore "Lithops" means "stone-like". This is a very good description of these plants, which avoid being eaten by blending in with surrounding rocks. ...