Dennis Mahoney, age 12, of Rensselaer, New York, for his question:

What exactly are air plants?

Some people mistake the air plants for parasites, such as mistletoe, that draw their food supplies from other plants. This notion is unfair because the true air plants use their hosts only as step ladders. Most of them live in dense forests and crowded jungles where air and light is screened from the lower vegetation by high canopies of dense foliage. They are smallish plants and in order to get their quota of air and sunlight, they must perch on the shoulders of taller plants. Botanists classify them as "epiphytes," a term meaning "on a plant."

Many mosses and lichens that seem to be sprouting from the trunks of trees in our wet north woods are classified as epiphytes. They perch themselves above the ground to get a fair share of light and moist air. The most glamorous air plants thrive in tropical jungles, adding their brilliant blossoms to the foliage of the high trees. Many of them are varieties of bromeliad plants. And the majority of the world's glamorous orchids are epiphyte air plants. Certain cactuses, ferns and liverworts also perch themselves on taller plants and live epiphyte lives.