30.

112 BOTANY

20. Describe the way in which a dicotylous stem grows in
thickness, and explain how it is that the stem shows
annual rings.
21. An oak stem continues to grow in thickness as long as the
tree lives, but the stem of a palm does not thicken
after it is once formed. Why is this?
22. Through what tissue does the water from the soil ascend
the stem from root to leaf? How could you show this?
23. What is meant by the translocation current? How could
you show through what tissues it travels?
24. What materials would you use for a lesson on "Stem
Modifications" to a class of children between the ages
of 11 and 13?
25. What is bark, and what purpose does it serve?
26. What are bud-scales? How could you hasten the opening
of buds? What risk is involved in doing this?
27. What are adventitious buds? Under what conditions do
dormant buds become active?
28. What is the difference between a flower bud and a
vegetative bud? Explain the relation that exists
between them.
29. In what parts of plants, in what forms, and for what
purposes are reserves of food accumulated? What
changes must certain of these reserves undergo in order
to become available?
30. Describe the different ways in which a plant may produce
vegetatively.
31. Draw a vertical section of an ordinary bud. Show clearly
the arching leaves and indicate the position of the
growing point.
32. What important precautions must be taken in the opera-
tions of budding and grafting? Can you suggest any
reasons why these precautions should be necessary?
33. Compare roots and stems, dealing with structure, tropisms,
appendages, and mode of growth.
34. What are the tests for starach, grape sugar, inulin,
cellulose, oil, solid protein? In what parts of plants
would you expect to find each of these substances
respectively?
35. Explain fully the advantages and disadvantages possessed
by climbing stems. Classify the different methods by
which plants climb.
36. What types of plant succeed best on the wind-swept sand
dunes? Give reasons.