arrangement, see all sedges. For 5-ranked (which is one of the commonest), see apple, cherry, pear, peach, plum, poplar, willow. For 8-ranked, see holly, osage orange, some willows. More complicated arrangements occur in bulbs, house leeks, and other condensed parts. The buds or "eyes" on a potato tuber, which is an underground stem (why?), show a spiral arrangement (Fig. 111). The arrangement of leaves on the stem is known as phyllotaxy (literally, "leaf arrangement"). Make out the phyllotaxy on six different plants nearest the schoolhouse door.
In some plants, several leaves occur at one level, being arranged in a circle around the stem. Such leaves are said to be verticillate, or whorled. Leaves arranged in this way are usually narrow: why?
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Fig. 111.—Phyllotaxy of the Potato Tuber. Work it out on a fresh long tuber.
Although a definite arrangement of leaves is the rule in most plants, it is subject to modification. On shoots that receive the light only from one side or that grow in difficult positions, the arrangement may not be definite. Examine shoots that grow on the under side of dense tree tops or in other partially lighted positions.
Suggestions.—55. The pupil should match leaves to determine
whether any two are alike. Why? Compare leaves from the
same plant in size, shape, color, form of margin, length of petiole,
venation, texture (as to thickness or thinness), stage of maturity,
smoothness or hairiness. 56. Let the pupil take an average
leaf from each of the first ten different kinds of plants that
he meets and compare them as to the above points (in Exercise
55), and also name the shapes. Determine how the various
leaves resemble and differ. 57. Describe the stipules of rose,
apple, fig, willow, violet, pea, or others. 58. In what part of
the world are parallel-veined leaves the more common? 59. Do
