In common speech, any plant which grows on the trunk or in the top of another plant is called an air-plant. The scientific term is Tillandsia. In horticulture, the term air-plant is usually applied to epiphytal orchids, tillandsias, and the like. Most of these grow upon old bark, perhaps deriving some of their nourishment from the bark, but most of it from the air and rain. They are not parasitic. They do not derive their support from the juices of the host.