Psilophytes are the only living vascular plants to lack both roots and leaves. Though they have been considered “primitive,” recent developmental and molecular evidence suggests that the group may actually be reduced from fern-like ancestors. Despite the uncertainty of their relationships, psilophytes do structurally resemble certain early vascular plants, and are used as a model for understanding the ecology of these plants. The psilophyte stem lacks roots; it is anchored instead by a horizontally creeping stem called a rhizome. The erect portion of the stem bears paired enations, outgrowths which look like miniature leaves, but unlike true leaves, the enations have no vascular tissue. These paired outgrowths lie immediately below the spore-producing synangia, which produce the spores. The synangia appear to be the product of three sporangia which became fused over the course of evolution, and are borne on the tip of a short lateral branch. This is another feature in which the psilophytes differ from other living vascular plants; all other such plants produce their sporangia on their leaves. When the synangia mature, they open to release yellow to whitish spores, from which the gametophyte plants will later emerge.The gametophytes are very small, usually less than two millimeters long. They are subterranean and saprophytic, getting their nutrition by absorbing substances dissolved in the environment.