Cathy MacIsaac, age 12, of Niagara Falls, Ontario, Canada, for her question:

Why can't a single holly tree bear berries?

A single girl is not expected to bear babies, though this can happen. A single holly tree is not expected to bear berries    and this can never never happen. The reason is that holly trees come in two sexes. One sex produces only male reproductive cells, the other produces only female reproductive cells. The parents must be rooted close enough together so that pollen from the male tree can reach the egg cells of the female.

The handsome couple wear their glossy evergreen leaves all year and their tiny green flowerets often go unnoticed in early summer. When the pollen begins to blow, some of its golden grains reach the female tree and fertilize the egg cells in its flowerets. Through the summer, the seeds develop inside bunches of green berries. These, as we know, turn bright red in time to add a merry burst of color to the Christmas decorations.