Epiphytic plants live on other plants without harming them or deriving nutrients from them. The majority of epiphytic species are found in the wild in humid tropical forests, where the main limiting factor is light. On a single tree in a tropical forest, one can find several dozen epiphytic plants, including orchids, tillandsias, ferns, and cacti, forming true biodiversity gardens within the tree canopies. Some orchids, for example, have two types of roots: some allow the plant to anchor itself to the branches of host trees, while others have a green epidermis, indicating photosynthetic activity taking place in them. In other species, the roots form a sort of network that accumulates fallen leaves from the overlying trees; this creates a fertile substrate from which the epiphytic plant obtains its nutrients. The stag's horn fern (Platycerium alcicorne) has photosynthetic leaves that resemble the antlers of a stag, as well as round or heart-shaped, cup-like leaves that anchor the plant to the host trunk. In some species of Bromeliaceae, the leaves are gathered in rosettes where water can accumulate; within these "air pools", insects and small amphibians find an ideal place to reproduce and complete their life cycle.
In the Botanical Garden, epiphytic plants are kept outdoors in the epiphyte area or in a greenhouse, depending on their temperature and humidity requirements.
Sistema Museale di Ateneo
