Study of a Woody Stem. 33 



or its scar. Carefully remove the scales one at a time until 

 you come to the very tender, real bud in the center, made 

 up of the beginnings of leaves on a stem which has imper- 

 ceptible internodes. The scales which you have removed 

 are evidently modified leaves, which do work very different 

 from that of normal leaves. We say of these winter-bud 

 scales that they are homologous with leaves.* 



Cut a thin cross-section of your woody stem. Note in 

 the center the pith, on the outside the bark, and between 

 them the wood. Cut another section near the upper end. 

 What forms the larger part of the old portion of the stem ? 

 of the young portion ? Does the pith grow any after the 

 stem is a few weeks old ? Cut a piece two or three inches 

 long from the base of the stem, and put the larger end into 

 a cup or short bottle containing a little red ink. [The 

 entire class might use one cup or goblet.] 



Provide for the next exercise at least one of the short, 

 rough twigs of a cherry-tree. Orchardists call them fruit 

 spurs. [See the next figure.] 



The simple microscope and a pair of needles, described 

 in the appendix, will be much needed in the following 

 exercises. 



*The primary organs of a plant are roots, stems, leaves, and hairs. All other 

 organs or parts are each homologous with one of these four. For example, pota- 

 toes, the tendrils of a grapevine, and the spines of a lemon-tree are homologous 

 with stems; the tendrils of a pea, the spines of barberry bushes, and the pods of 

 beans are homologous with leaves; the prickles of rose-bushes, the hooks on 

 cockleburs, and the stings of nettles are homologous with hairs. To find the 

 proofs of these statements is very interesting, but not easy. 



