Bark Protects the tree from injury, insects, and pathogens. Inner Bark Layer of cells that transports nutrients from leaves to root cells. Cambium Growing part of the tree. Produces phloem and xylem and is seldom more than 10 cells thick. Severe damage to the cambium can kill a tree. Sapwood Transports water from the roots to the leaves. In the second picture, green moss lives on the excess moisture found in sapwood. Heartwood Gives strength to the stem. In redwoods, the heartwood increases in size and eventually makes up the largest portion of the total trunk volume. Notice that in both pictures the heartwood supports no living organism. (The "white mark" in the second picture is whitewash from a bird).
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