represented stipules they would, as a rule, be in pairs, which is not the case. Moreover, Clos's view could not, of course, apply to the bracts of exstipulate species. FIG. 339. SEEDLING OF SPECIES OF PSYCHOTRIA. Nat. size. S, stipule. I think, then, as already stated, we must conclude that stipules are an integral part of the leaf; that leaflets are portions of the leaf-blade; and that, if we consider the leaf-blade as a part separate from the petiole, we must regard the leaf as consisting of four parts, viz.: 1. The blade. 2. The petiole. 4. The base. Perhaps, however, it would really be more consistent with the facts to regard it as composed of two parts: 1. The upper part, or petiole, generally provided with a leaf-blade; and 2. The base, which also is often provided with a pair of stipules. 223 CHAPTER IX SUMMARY THE BUD THE bud is a young shoot-that is, a stem or branch with its rudimentary leaves closely packed together. It is normally situated either at the summit of the stem or in the axil of a leaf. The young leaves require protection against too great cold, heat, drought, or moisture, too vivid light, and the attacks of animals and plants. This is effected in various ways. The scales which protect the winter-buds fall into at least eight categories: 1. Pedestals of last year's leaves, as in Pyrus Aria. 2. Stipules of last year's leaves, as in Magnolia. 3. In many cases the young leaves are protected by modified leaves, as, for instance, in Willows and Lilac. 4. In others the protection is afforded by leaf-stalks, the leaf not being developed, as in Maples and the Sycamore; 5. In others by the leaf-base, as in the Rose, Portugal Laurel, &c.; 6. In others, again, by stipules, as in the Beech, Oak, Elm, Poplar, &c. ; 7. In others by pairs of stipules, as in the Elm, Spanish Chestnut, &c.; 8. Or by two connate stipules, not, however, belonging to the same leaf, as in the Hop. In many species the protection thus afforded is further enhanced (1) by the presence of a gummy or resinous secretion, as in the Horse Chestnut, Plane, Alder, Conifers; or (2) by furry hairs, as in the Plane, Horse Chestnut, Vine. STIPULES Stipules are normally more or less leaf-like structures at the base of, or just below, and one on each side of, the leaf-stalk. They are very variable in size and appear ance. A typical leaf may either be considered to consist of four parts: 1. The leaf base. 2. A pair of stipules. 3. The leaf-stalk or petiole. 4. The leaf-blade, which for shortness is often called the leaf. Or, and perhaps more philosophically, of two parts: 1. A leaf-base, which may or may not develop stipules. |