Page:Popular Science Monthly Volume 3.djvu/335

Rh of its growth; and the rate thus ascertained may be applied to other trees of its kind whose diameter is known, although its woody layers he inaccessible. In this way the age of many trees has been estimated. The relation between the age of a tree and its annual rings was first noticed and applied by Montaigne, in 1581.



But this method of ascertaining a tree's age does not apply to the class Endogens, in which the growth is internal, as shown in Fig. 2.