The base of Fig. 35 is much less tapering than Fig. 31. You will find all degrees, in this respect, from very blunt to very tapering. You will also be likely to find many leaves to which none of these pictures apply. In such cases you may write, I do not know, in the schedule, and wait till further exercises have shown you how to describe them. sources shall be as extensive as possible. Teachers should therefore press beginners and negligent pupils about looking for new specimens. After a little time, such pressing will, in most cases, be unnecessary; for, when the interest and pride of a child are awakened by success in describing plants, he will take increasing pains to find new subjects for description. EXERCISE VIII. Apices. THE APEX of a leaf is its top, or free end. FIG. 36. FIG. 37. FIG. 38. FIG. 39. FIG. 40. A j Q A A The Apex of a leaf may be: ACUTE. Simply ending with a point. Fig. 36. Fig. 37. OBTUSE'.-Blunt. Fig. 38. TRUN'CATE. Cut off at the apex. Fig. 39. Fig. 40. FIG. 41. FIG. 42. FIG. 43. FIG. 44. OBCOR'DATE.—Heart-shaped at the apex. Fig. 41. Fig. 42. MU'CRONATE.-Tipped with a stiff, sharp point. Fig. 43. CUS'PIDATE.-Suddenly ending with a sharp, slender point. Fig. 44. The words acute, acuminate, and obtuse may be used to describe bases as well as apices, and, when we wish to say that a shape is less acute or less acuminate than Figs. 36 and 37, we may say it is sub-acute or sub-acuminate, as in the schedule to Fig. 45. FIG. 45. Parts? SCHEDULE FOURTH, DESCRIBING FIG. 45. Blade, Petiole, Stipules. Venation? Net-veined, Feather-veined. Margin? Serrate. Base? Obtuse. Apex? Sub-acute. EXERCISE IX. Forms of Lobes. THE most striking difference in lobed leaves is the one seen in contrasting Fig. 46 with Fig. 47. It will be quite enough to ask of young beginners that they report whether the lobes of a leaf are rounded or acute. FIG. 46. FIG. 47. Rounded Lobes. Acute Lobes. But there may be older pupils who could profitably go further in observing the lobes of leaves. They vary much in size and shape, and are rarely all alike upon the same leaf. The lobe at the apex of a leaf is called the Terminal lobe, and is usually unlike all the others. The two lobes at the base are called basal lobes, and these also are usually unlike all the rest; for any pupils who would desire fuller observations upon lobes, a schedule might be prepared with two additional lines and the two questions, Terminal? and Basal? added to the present one. It might be well in such a case to give the number of lobes upon the leaf, along with their form, in answer to the question Lobes? While the peculiarities of the terminal and basal lobes would be given after these questions. In dealing with lobed leaves, you will not always find the base and apex so easily described as is Fig. 53, in the schedule. If they give you trouble, you may omit the questions, Base? and Apex? |