From the two newly formed thin-walled cells of each radial row one remains thin walled and rich in protoplasm, and in a condition capable of division; the other becomes transformed into a permanent cork cell. Thus arises, usually parallel to the surface of the organ, a layer of cells capable of division, which continues to form new cork cells, the cork cambium or layer of phellogen. In general this is the innermost layer of the whole cork tissue, so that the production of cork advances outwardly and new layers of cork are constantly formed out of the phellogen on the inner surface of those already in existence. When in this manner a continuous layer of cork arises, steadily increasing from the inside, it is termed “periderm.” As the epidermis is at first replaced by the periderm, so in turn is this replaced by cork (the dead tissue). The development and configuration of the cork cells may change periodically during the formation of periderm. Alternate layers of narrow, thick-walled and broad, thin-walled cork cells are formed; the periderm then appearing stratified, like wood, showing annual rings as in the periderm of the Quercus Suber, Betula Alba, etc.” Mr. Sacks, as a botanist, has clearly set forth the explanation of the formation of the periderm of the Quercus Suber in the foregoing, and although the story of the life producing this formation would be an acceptable sequel to this explanation, it would in no wise assist in the ultimate findings, and therefore it is dispensed with. Mr. William Anderson, in a paper read at the Royal Institution of Great Britain in 1886, has the following to say on cork formation, which is very interesting: “In considering the properties of most substances, our search for the cause of their properties is baffled by our imperfect powers and the feeble instruments we possess for investigating molecular structure. With cork, happily, this is not the case; an examination of its structure is easy and perfectly explains the cause of its peculiar and valuable properties. All plants are built up of minute cells of various forms and dimensions. Their walls or sides are composed chiefly of a substance called cellulose, frequently associated with lignine, or woody matter, and with cork, which last is a nitrogenous substance found in many portions of plants, but is especially developed in the outer cork of exogenous trees, that is, belonging to an order, the stems of which grow by the addition of layers of fresh cellulose tissue outside the woody part and inside the bark. Between the bark and the wood is interposed a thin fibrous layer, which in some trees is very much developed. The corky part of the bark which is outside is composed of closed cells, exclusively, so built together that no connection of a tubular nature runs up and down the tree, although horizontal passages radiating toward the woody parts of the tree are numerous. In the woody part of the tree, on the contrary, and in the inner bark, vertical