"Where do we find the newly-formed wood in the stem?" "The last-formed layer of wood is always found on the outside, just under the bark," said Willie. "It is called the sap-wood. It is formed from the sap which has passed upwards through the stem and leaves. The sap, after it has flowed back from the leaves, is deposited in this part ofthe stem, where it forms the new layer of sap-wood.""A very good answer, my boy," said Mr. Wilson. "This sap-wood is at first soft, pulpy matter, and while in that state it affords a convenient channel for the upward passage of the sap, which can no longer rise through the dead flattened cells of the pith and the medullary rays."Lesson 08
Joints
In our lessons on the human skeleton we found that some of the bones, such as those of the skull and face, are not meant to move. These bones are united firmly together.
