field for study and experiment.

3. _Structure of Stems_.--Let the pupils collect a series of branches of
some common tree or shrub, from the youngest twig up to as large a branch
as they can cut, and describe them. Poplar, Elm, Oak, Lilac, etc., will be
found excellent for the purpose.

While discussing these descriptions, a brief explanation of
plant-structure may be given. In treating this subject, the teacher must
govern himself by the needs of his class, and the means at his command.
Explanations requiring the use of a compound microscope do not enter
necessarily into these lessons. The object aimed at is to teach the pupils
about the things which they can see and handle for themselves. Looking at
sections that others have prepared is like looking at pictures; and, while
useful in opening their eyes and minds to the wonders hidden from our
unassisted sight, fails to give the real benefit of scientific training.
Plants are built up of cells. The delicate-walled spherical, or polygonal,
cells which make up the bulk of an herbaceous stem, constitute cellular
tissue (_parenchyma_). This was well seen in the stem of the cutting of
Bean in which the roots had begun to form.[1] The strengthening fabric
in almost all flowering plants is made up of woody bundles, or woody
tissue.[2] The wood-cells are cells which are elongated and with thickened
walls. There are many kinds of them. Those where the walls are very thick
and the cavity within extremely small are _fibres_. A kind of cell, not
strictly woody, is where many cells form long vessels by the breaking away
of the connecting walls. These are _ducts_. These two kinds of cells
are generally associated together in woody bundles, called therefore
fibro-vascular bundles. We have already spoken of them as making the dots
on the leaf-scars, and forming the strengthening fabric of the leaves.[3]