TLDR
“The stalk is the common support of the plant’s various parts. It is called annual or herbaceous when it lives only one year, as in the potato, spinach, parsley, and all forms of vegetation that from their soft structure belong to the class of herbs. Ligneous is the name given to the stalk when, designed to live for a greater or less number of years, it is made of strong woody fibers, such as we find in the trunks of trees.
“Let us make a clean cut through any tree-trunk, that of an oak for example. We shall find it divided into three parts: in the center the pith or marrow, very slightly developed; around the marrow the wood proper; and, finally, on the outside, the bark. A closer examination shows that the wood is formed of concentric layers which are indicated in the cross-section by a series of circles having the marrow for a common center. These layers are called ligneous zones or, since one is formed every year, annual layers. During the summer there is a downward flow, throughout the tree, of a peculiar liquid, the descending sap, which constitutes the fluid nourishment of the tree. This liquid runs between the wood and the bark and becomes, little by little in its course, [71]on one side a layer of wood which attaches itself to the outer surface of the preceding year’s layer, and on the other side a thin sheet of bark which is added to the inner surface of the bark already formed.via the TL;DR App
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Written by jeanhenrifabre | I was an entomologist, and author known for the lively style of my popular books on the lives of insects.