A plant pretending to be a rock
Camouflage is common in animal with many different elaborate disguises concealing many different types of animals from their various predators or sometimes prey items. While plants do sometimes mimic other poisonous plants or they may draw attention to their thorns they tend not to camouflage. Animals commonly use patterns and colour similar to the vegetation to hide themselves, but what backdrop could a plant camouflage into? Lithops is a genus of plant which specialises in camouflaging itself in stony deserts. They are commonly known as Living stones or pebble plants.
The rock-like top of the plant which you can see there is actually a highly modified leaf. Most of the plant is underground. It extends small stalk above the surface which grow a pair of semi-fused leaves which look like a rock. I know what you're thinking, aren't leaves green because of their chlorophyll? and don't they need that for photosynthesis? The answer is yes and yes. These leaves are actually translucent and enough light gets through them to reach the inside of the plant where all the real photosynthesis goes on.
This is a pretty good system until it comes time to pollinate the flowers. Like many plants they have mechanisms to prevent self-pollination so they need other plants to reproduce. There is just no way to do this without becoming a bit more obvious to insects, and potentially insect predators for the short period in which they are in flower.
Lithops is endemic to arid and semi-arid areas of southern Africa.
Lithops are commonly included with cactuses in plant stores and gardening blogs etc... They are not in the cactus family, but their family Aizoaceae are a predominantly arid family and is in the same order, Caryophyllales.