Certain leaves possess a remarkably abnormal shape; for example, stone-crops have cylindrical leaves; if the leaf of an agave is cut across, the section is triangular; leeks, again, are tube-shaped; the central cavity being due to the rapid growth of the outer tissue. These leaves are all juicy or succulent; certain other leaves are leathery, that is, they have a harder and thicker epidermis than the succulent leaves, and may last for several years, as, for example, in the holly and box. Spines and tendrils are modifications of leaves, or parts of leaves. The tendrils are formed out of entire leaves, midribs, leaflets, or stipules. Both spines and tendrils, however, may be modified branches of the stem. In buds the leaves are packed or folded in various ways. This is best seen before the buds are opened in spring. The buds may then be pulled carefully to pieces, and in this way the manner in which the leaves are folded can be studied. We now come to the flower. Flowers consist of leaves modified in different ways. Take, for example, the flower of the orange. The flower will be seen to be borne on a short branch which serves as the stalk, and is distinguished by the name of peduncle (from Lat. _pedunculus_, little stalk). It will be seen that there are no internodes between the flower-leaves. The lowest and outermost part of the flower forms a little cup having upon its margin fine small teeth, indicating the number of leaves which are joined together so as to form the cup or calyx. These leaves are named (from Lat. _calyx_, a covering; Greek _kalyx_, from _kalyptein_, to cover) the calyx-leaves, or sepals (French _sépale_). Although they are united in the flower of the orange, they are often separate in other plants. In the sacred Lotus or Padma or Pudma of India the sepals are separate or free. The leaves immediately inside the calyx are usually five in number. They are erect, or only slightly curved, and do not grow together like the leaves of the calyx. They are white and wax-like. These leaves form together what is termed the corolla, and the separate leaves of the corolla (from Lat. _corolla_, a little wreath) are termed petals (from Greek _petalon_, leaf). In the case of the orange the petals fall early away. If the calyx and petals are carefully removed, the next part of the flower can be observed. This series of flower-leaves differs very much in structure from both sepals and petals. Each leaf of this series consists of a linear stalk-like portion, bearing an upper somewhat long and grooved head. The stalk is named the filament, and the oblong head is named the anther (Greek _anthos_, a flower). The stalk and the head together form what is called the stamen (Lat. _stamen_, [Greek _histanai_, to stand] fibre; literally, the warp in the upright loom of the ancients). The stamens of the orange are rather shorter than the petals, and are united to each other.