Infinite variations

Mirror, mirror, on the wall, who's the fairest of them all? We can all be grateful for the fact that trees bear a wide variety of flowers. Yet the flowers of two related species can be very different. Those of a Norway maple, for instance, don't look anything like those of a sugar maple, as they have petals (making them more visible to certain insects).

But no matter how showy all these different flowers may be, they aren't designed for our pleasure. The flower, which is the result of millions of years of evolution, is the organ used by trees for sexual reproduction – and, consequently, is their main source of genetic mixing.