7. Blackberry leaves.—Gather several leaves from a blackberry bush. Notice that in addition to the “saw cuts,” the margins of some are cut into slightly, while others are divided quite to the midrib, the leaf being thus cut into two or more leaflets. Select specimens which form a gradual series between the “simple” leaf and the “compound” leaf (consisting of three or five leaflets) and draw them. 8. The horse chestnut leaf.—Draw the compound leaf of the horse chestnut, and draw an even curved line joining the points of the leaflets. You can imagine that the compound leaf may have been formed by a leaf of this shape being cut into until it was divided into seven complete leaflets. 9. The rose leaf.—Draw an imaginary simple leaf such as may have been the original form from which the compound leaf of the rose was derived. Notice the difference in the arrangement of the main veins of the leaves of the horse chestnut and the rose. Does this account for the leaflets coming off at the sides of the midrib in the rose leaf, and springing from one point, like fingers from the palm of the hand, in the case of the horse chestnut? 10. Sycamore and ivy leaves.—If the large indentations in these leaves were continued to the midrib, would the compound leaves thus formed be of the type of the rose leaf or of that of the horse chestnut leaf? 11. The leaf-stalk.—What attaches the leaf-blade to the stem or branch of the plant? Can you see signs of the main veins joining the top of the leaf-stalk? Do you know any plant with the blades of the leaves fixed directly on the stem, i.e. without any leaf-stalks? [Pg 39] 12. Stipules.—Examine the rose leaf again and notice the two leaf-like outgrowths at the bottom of the stalk. These are called stipules. Make a list of as many leaves as you can find which have stipules. How many leaves can you find with a sheath at the bottom of the stalk? 13. The leaf of the sweet pea.—Notice the large stipules of this compound leaf (Fig. 28). What are the tendrils? Do you think they may be mainly the larger veins of the upper leaflets? Is the leaf of the type of the rose or of the horse chestnut leaf? 14. Other compound leaves.—Compare and contrast ash, lupine, woodsorrel, strawberry, and other compound leaves with those of the rose and horse chestnut. A leaf.—The leaves of different plants vary much in size and shape, but in general a leaf is a thin, broad, and more or less oval blade of green colour, attached by a leaf stalk to the stem or branch. In some cases, however, the leaf stalk is absent and the blade is attached directly to the stem or branch.