Leslie Olson, age 11, of Vauxhall, Alta., Canada, for her question:

HOW MANY DIFFERENT PALM TREES ARE THERE?

Ages ago, when the worldwide climate was warmer, palm trees thrived in Canada and almost everywhere else on earth. Later, most of them retreated to the tropics. Those of us who live in cool climates know about coconut and date palms and perhaps a few others. Actually there are more than 2,600 different palm trees.

The average palm has a tall, stately trunk topped with a handsome crown of enormous green leaves. It may survive in arid deserts, high on a blustery mountain or up to its ankles in tidal sands. But it cannot abide cold winters. It may be a 3 foot midget or a giant, more than 100 feet tall. A few types have pencil slim stems and twine like vines, hundreds of feet through the jungle trees.

Aside from being very handsome, each of more than 2,600 different palms has something to give to the world. As tropical and semitropical evergreens, they provide shade where shade is needed most. And through the sunny hours, their greenery pours fresh oxygen into the air. Their shady boughs provide homes, roosts and food for an assortment of birds and other animals.

But most of their generous gifts are reserved for people. various date palms have been cultivated for ages. Certain wild palms donate a sugary syrup called toddy. Other species produce hardheaded coconuts.

Many palms yield rich oils used for cooking and making margarine. Others have leaves coated with wax, which is used to make polishes for shoes and furniture. Many species yield tough fibers, used to make string and rope. Wider palm fibers are woven into hats and baskets. The list of useful palm products goes on and on  and many of them are taken for granted in our daily lives.

In the tropics various palms provide posts to build walls, leafy roofing thatch and twines to tie the pieces together. Young palm leaves provide leafy vegetables. Other types yield dates, coconuts and sweet beverages. Palm wax is used to make candles. There are palm oils for cooking and making soaps  and even tough palm nuts for carving buttons and figurines.