Atoms, cars and ecosystems all have parts that together make up the whole. Trees havethe perfect number of parts to survive and thrive in the environment. Each part has aprimary job to perform. Everyone can see the biggest tree parts. Trees have twigs and branches that support theleaves and buds. The stem supports the branches. The roots support the stem. Beneath the dead bark layers are living cells that produce bark. Beneath these cells is alayer of transport cells called the phloem. This is sometimes called inner bark. The inner portion of a branch, stem or root is made of xylem. The xylem area is acombination of parts that act as transport pipes, strength fibers and living helper cells. The tree parts few people notice are small, internal components. When you cut across abranch with a saw, you cut many tissues or parts. The first part damaged is the bark. Bark helps the tree conserve precious moisture by slowing water’s escape into the air. Butit must also allow for oxygen to move inward and carbon dioxide to escape. Both phloem and xylem come from the same mother cells. These special mother cells arean area called the cambial zone, a major growth and reaction center in a tree. Bark is a good insulator, too. It protects the tree from sudden changes in temperature andfrom heating caused by sunlight. Phloem is responsible for moving food and other growth materials made in the leaves toall the other parts in a tree. It’s the major transport highway in a tree. Xylem pipes transport water, essential elements and growth materials from the roots to theleaves. The fiber cells provide strength, keeping the stem upright against gravity and wind.The living helper cells store food, react to damage and transport needed growth materialsfor short distances. Those are the parts people most easily damage, too. The bumps, bruises and nicks of dailylife, many of which we may consider minor, can add up to be life-threatening in a tree. Bark’s the first barrier to breach, too, when a pest attacks a tree. Without healthy bark,trees would be dry, suffocated and diseased. When you cut into the wood, the outer protection layer (bark), food transport connections(phloem) and growth layer (cambial zone) are all severed. Remember, the most exteriorparts of a tree are responsible for its life. Bark is an amazing material. The outside bark is made of dead, air-filled cells that havebeen flattened and sealed with a waterproof material. The phloem is made by special cells that split apart, producing two new cells — one to theoutside and one to the inside. The new cells split off to the outside become phloem. Theones split off to the inside become xylem, the wood inside a tree. This cambial zone responds to changes in the environment by producing more or fewercells of different types and with different characteristics. It’s responsible for a tree’s yearlyexpansion in girth. Think of bark as an oil-covered canvas coat. It’s lightweight. It floats in water — corks aremade from the bark of an oak tree. If you don’t know tree parts and how they work, it’s hard to understand a whole tree. Atree is a single, highly integrated and specialized creature. Trees must stand against an environment trying to knock them down and neighbors tryingto consume them. You can help them survive and thrive by appreciating their parts,knowing how they work and preventing tree damage.