21.   Those trees produce such now-obscure varieties as Arkansas Black and Mammoth Blacktwig.

22.   Trees produce several different kinds of roots, he said.

23.   Without water, however, the trees produce fewer sugars and use them up, giving the remaining leaves a dull color.

24.   Once groves are replanted, it takes at least four years before new trees will produce fruit.

25.   The olive tree will produce olives year after year for hundreds, possibly thousands of years.

26.   The trees produce light, strong wood that is used to make furniture and musical instruments such as violins and dulcimers.

27.   The trees produce a small yellow flower pollinated by bees.

28.   He said oxygen produced by trees from reforestation will combat toxic gases.