Non-vascular plants are plants without a vascular system consisting of xylem and phloem. Although non-vascular plants lack these particular tissues, many possess simpler tissues that are specialized for internal transport of water.

Non-vascular plants do not have a wide variety of specialized tissue types. Mosses and leafy liverworts have structures that look like leaves, but are not true leaves because they are single sheets of cells with no cuticle, no stomata, no internal air spaces and have no xylem or phloem. Consequently, they are unable to control the rate of water loss from their tissues and are said to be poikilohydric.