starchy food stored in the carrot becomes soft and soluble, and the supply
of proper food and the warmth of the room make the leaf-buds able to grow.
It is also a pretty illustration of the way in which stems always grow
upward, even though there is enough light and air for them to grow
straight downwards. Why this is so, we do not know.


3. _Differences between the Stem and the Root.--_Ask the pupils to tell
what differences they have found.

_Stems_. _Roots_.

Ascend into the air. Descend into the ground.
Grow by a succession of similar Grow only from a point
parts, each part when young just behind the tip.
elongating throughout.
Bear organs. Bear no organs.

There are certain exceptions to the statement that roots descend into the
ground; such as aërial roots and parasitic roots. The aërial roots of the
Ivy have been mentioned. Other examples of roots used for climbing are
the Trumpet Creeper _(Tecoma radicans)_, and the Poison Ivy _(Rhus
Toxicodendron)_. Parasitic roots take their food ready-made from the
plants into which they strike. The roots of air-plants, such as certain
orchids, draw their nourishment from the air.

The experiment of marking roots and stem has been already tried, but it
should be repeated. Repetition of experiments is always desirable, as it
fixes his conclusions in the pupil's mind. The stem grows by a succession
of similar parts, _phytomera_, each part, or _phyton_, consisting of node,