Answer: The phloem tissue layer
Explanation: The phloem tissue of a plant is one of the vascular tissues of higher plants responsible for the conduction or transportation of photo-synthetically manufactured food (usually in the form of sugar) round the body of the plant to the various tissues and organs that require it.
The tissue moves food materials from their source of manufacture, usually the leaf, to other parts of the plant. Hence, in order to extract the syrup from the maple tree, the phloem layer must be tapped into.