Whisk ferns (Class Psilotopsida) are not true ferns, but plants with shrub-like appearance that are closely related to ferns. Unlike ferns, they lack leaves, but have very unique structures known as enations (or synangia). Enations are small, scaly, ball-like outgrowths extending from the stem which harbor the spores. While these structures are leaf-like, they are not considered leaves (microphylls or mesophylls) due to the lack of any vascular tissue, even though the stems do have tracheids. Whisk ferns do not have true roots and are held to their substrate by rhizoids, extremely short anchoring structures. These rhizoids have a mutualistic relationship with mychorrhizal fungi that help plants absorb water and nutrients.