Here's how it happens:

* Swampy Environments: Swamps are ideal for coal formation because they are rich in plant life and have a lot of water.

* Plant Accumulation: Over time, layers of dead plants, like ferns, mosses, and trees, build up on the swamp floor.

* Sedimentation: As the swamp fills with water, sediment (like mud and sand) is deposited on top of the plant debris.

* Pressure and Heat: Over millions of years, the weight of more sediment and the increasing heat deep underground transform the plant material. The oxygen is squeezed out, leaving behind mostly carbon.

* Coal Formation: This process forms different types of coal, depending on how much heat and pressure the plant material experiences.

So, the living plants in a swamp that become coal are things like:

* Ferns

* Mosses

* Trees (especially those adapted to wet environments, like cypress trees)

This process is a fascinating example of how ancient life can be transformed into a valuable energy source!