Mosses are primitive plants. They lack two parts that other plants have: they have no roots or flowers. Mosses attach themselves to the ground or a tree trunk with small rhizoids. It collects water with its whole body, like a sponge. 

Because mosses do not have strong stems, they cannot grow very tall. This is why mosses can only be found growing near the ground or on tree trunks in wet locations. 

Mosses can often cover the forest floor completely, especially in spruce forests. Mosses reproduce by releasing spores.