An epiphyte is a plant growing on another plant as a physical support, without obtaining its food by drawing from that support plant as a parasitic plant does. The support can place the epiphyte above the ground, but it does not eliminate requirements for water, mineral nutrients and, in a photosynthetic epiphyte, light. Tillandsia usneoides is a familiar epiphyte in Bromeliaceae.[ref]
Physical support and water supply are separate problems. In Tillandsia usneoides, surface trichomes help collect and distribute water rather than relying on a conventional ground-rooted supply. A study compared water movement across shoots with intact trichome wings and shoots without those wings, using fluorescent droplets to reveal surface spreading.[ref]
Domino-like water transport on Tillandsia through flexible trichome wings by Nami Ha and others. Results and Figure3: external water transport with/without wings
For an illustrative classification exercise, record three facts independently: what supports a plant, where its water comes from, and whether it draws nutrients directly from another living plant. Growing on a branch answers only the first. Nor does a shared epiphytic habit place two plants in the same taxonomic family; habitat and ancestry are different kinds of biological information.
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