Dr. Goodale says of this experiment,--"Let a young seedling of corn be
grown on damp paper in the manner described in No. 1,[1] and when the
longest root is a few centimetres long let it be marked very carefully by
means of India ink, or purple ink, put on with a delicate camel's-hair
pencil just one centimetre apart. Plants thus marked are to be kept under
favorable conditions with respect to moisture and warmth, so that growth
will be as rapid as possible. The marks on the older part of the root
will not change their relative distance, but the mark at the tip will be
carried away from the one next it, showing that the growth has taken place
only at this point. Such experiments as the one described are perfectly
practicable for all classes of pupils except the very youngest. How far
the details of these experiments should be suggested to the pupils, or
rather how far they should be left to work out the problem for themselves,
is a question to be settled by the teacher in each case. The better plan
generally is to bring the problem in a very clear form before the whole
class, or before the whole school, and ask whether anybody can think of a
way in which it can be solved; for instance, in this case how can it be
found out whether roots grow only at their tip or throughout their whole
length. If the way is thought out by even a single pupil the rest will be
interested in seeing whether the plan will work successfully."

[Footnote 1: Concerning a Few Common Plants, page 25.]

I have been more successful in pricking the roots than in marking them
with a brush.

The caulicle can be proved by the manner of its growth to be of the nature
of stem, not root. The main root grows from its naked end. Roots can also
grow from the sides of the caulicle, as in Indian Corn. In this, it acts