SIV INTRODUCTORY LESSONS. 
SECTION 2.—THE STRUCTURE OF PLANTS. 
Stems. While awaiting the development of germs in your experi- 
mental garden, you can study plants which have already reached maturity 
in wild gardens. Go out and dig up the first plant—not too large—that 
you find in blossom. I will suppose that you have found the very com- 
mon Filaria (also called Pin-clover; and children call the curious seeds 
with twisted tails, clocks). Its parts are Roots, Stem, Leaves, and Flowers. 
(Some time, if you continue studying Botany, it will be proved to you 
that flowers are forms of stems, or stem-branches.) 
Crush the stem. Itis made up of stringy fibers and a soft sub- 
stance filled with juice. The former is generally called Fibrous Tissue 
or Wood ; the latter, Cellular Tissue. The lower part of the stem and 
the upper part of the root—the older portions of the plant—contain 
more wood than the branches and the rootlets, while the leaves have only 
net-like skeletons of wood. It would be interesting to study these tissues 
with the aid of a microscope, and thus become acquainted with the inner- 
most structure of plants; but for the present it will be sufficient if you 
can distinguish, in a general way, wood from cellular tissue. 
Cut the stem squarely across near the upper end, and from one 
piece take a thin slice. Stick this on a pin and hold it up to the light. 
It is nearly transparent, except a green ring of skin outside and a ring 
of white dots inside. The latter are cut ends of woody fibers which run 
lengthwise of the stem. Make a similar section of the lower part of the 
stem and you will find a continuous ring in place of the dots, showing 
that in the older part the fibers have become so numerous as to form a 
hollow cylinder of wood. The inclosed cellular tissue is called the Pith. 
Exogens and Endogens, If the stem lives year after year there will 
be added successive layers of wood outside of the first one. Such stems 
are woody, and if they grow many years become Bushes, Shrubs, or Trees. 
Plants that grow in this way are called Mogens. Examine Asparagus, 
Soap-root, Iris, or any Lily and you will find the wood fibers scattered 
irregularly through the stems. ‘These plants are Zndogens. All our native 
