Nancy Madden, age 11, of Fredericton, N.B., Canada for her question:

Do cashew nuts grow in shells?

Cashew nuts have not one, but two shells. But both shells are removed before the sweet, tasty nut meats are sent to market. What's more, the double shelled nut grows attached to an apple type fruit. And this remarkable contraption grows on a huge, leafy evergreen tree of the tropics. Its sweet sour apples can be eaten raw or made into jams and jellies.

The cashew nuts need special processing because the space between their two shells contains a bitter, blistering oil. It so happens that the cashew tree is a large relative of poison ivy. Hence its shells must be removed and the nuts roasted before they go to market. The irritating oil completely evaporates in the heat. Sometimes it is recap¬tured and used to make insecticides. A very different sweet oil may be squeezed from the nuts for cooking and salad dressings. And the milky sap from this most useful tropical tree may be used in inks and varnishes.