I believe you might be referring to an Osage Orange Tree. See Related Links to see if I am correct.
An unripe black walnut.
It indicates that the tree is starting to rot and that there is fungus inside it.
It could be "Oak apples" which are galls on the trees made by the gall wasp. Another possibility is fungus. Answer They are definitely galls not fungus. I have golf-ball sized green pods on oak tree that are NOT galls.They are hollow except for what looks like a very small green flower inside.I'm clueless as to what they are.
it's brown outside because of the bark, it is green on the inside because all the cells are still alive.
Not enough information to answer with any degree of accuracy
coconut tree
A magic crocodile tongue got into the tree it was growing on.
To find an Apricorn tree, you need to look for a fairly small tree with a colored ball on top. The ball cam be green, black, pink, red, white, and blue. The easiest tree to find is on the west side of Kurt's house in Azalea Town. The ball will be white. To pick the Apricorn, stand facing the tree and press the A button on you DS.
A large, fast-growing evergreen with bluish green leaves and flowers. The tree can grow to 375 - 480 ft (125 - 160 m).
During the 1981 Benson and Hedges International, Langer hit his second shot into a tree by the 17th green. Famously, Langer climbed the tree and played his third shot, knocking the ball onto the green. Langer missed his putt for par and went on to finish second in the tournament.
A yew tree is a small, coniferous trees that are relatively slow-growing. The long-lived trees have reddish-bark, and flat, dark green leaves.
I believe it is the catelpa tree spelling is probably wrong but is pronounced this way.
A Christmas tree is an evergreen that keeps its green needles all year round. A maple tree is deciduous. It loses its leaves in the autumn and is naked all winter, growing new leaves in the spring.