Non-vascular plants are plants that lack water-conducting vessels in their tissue known as tracheids. These are often considered the "lower" plants. Strictly speaking, these include the green algae, the Bryophyta, the Hepatophyta, and the Anthocerophyta. However, in common usage, it generally is used to refer to the non-vascular complex plants, which are the above groups minus the green algae. These plants generally are haploid, with the only diploid part being the sporangia. Because these plants lack the water-conducting tissues, they fail to achieve the structural complexity and size of vascular plants.

"Lower plants" is also often used to refer to non-vascular plants and ferns and fern allies. The term "lower" refers to these plant's primitiveness as the earliest plants to evolve, not necessarily their lack of sophisticated functionality.