Outlines of Lessons in Botany, Part I; from Seed to Leaf by Jane H. Newell
page 91 of 105 (86%)
page 91 of 105 (86%)
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We have studied leaves as cotyledons, bud-scales, etc., but when we speak of _leaves_, we do not think of these adapted forms, but of the green foliage of the plant. 1. _Forms and Structure_.--Provide the pupils with a number of green leaves, illustrating simple and compound, pinnate and palmate, sessile and petioled leaves. They must first decide the question, _What are the parts of a leaf_? All the specimens have a green _blade_ which, in ordinary speech, we call the leaf. Some have a stalk, or _petiole_, others are joined directly to the stem. In some of them, as a rose-leaf, for instance, there are two appendages at the base of the petiole, called _stipules_. These three parts are all that any leaf has, and a leaf that has them all is complete. Let us examine the blade. Those leaves which have the blade in one piece are called _simple_; those with the blade in separate pieces are _compound_. We have already answered the question, _What constitutes a single leaf_?[1] Let the pupils repeat the experiment of cutting off the top of a seedling Pea, if it is not already clear in their minds, and find buds in the leaf-axils of other plants.[2] [Footnote 1: See page 31.] [Footnote 2: With one class of children, I had much difficulty in making them understand the difference between simple and compound leaves. I did not tell them that the way to tell a single leaf was to look for buds in the axils, but incautiously drew their attention to the stipules at the base of a rose leaf as a means of knowing that the whole was one. Soon after, they had a locust leaf to describe; and, immediately, with the |
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