THE STEM, when seen in transverse section, has its vascular bundles arranged in a ring; in reality, however, they form a kind of cylindrical network in the stem; the bundles are open, and thickening takes place by means of a cambium; annual rings are formed in the perennial stems. There is a rich and very varied form of _branching_. The two first leaves of a shoot (fore-leaves) are placed nearly always to the right and to the left; the same arrangement is found in the two first leaves developed on the flower-stalk, and these are, as a rule, the only two; they are found below the calyx and are usually termed the “_bracteoles_.” It has become customary to indicate the bracteoles by the letters α and β, according to their sequence of growth, and in that sense these letters will be employed in the following diagrams. THE ARRANGEMENT OF THE LEAVES varies very much; there is also a great variety of shapes in the leaves and their venation, but the linear leaves, with parallel venation, so frequent in the Monocotyledons, are seldom met with, as also the large sheaths (though the sheath is well developed in the Umbelliferous plants); stipules occur much more frequently. THE FLOWER is most commonly cyclic, but acyclic or hemicyclic forms also occur. The type which may be taken as a basis consists in the majority of instances, as in the Monocotyledons, of 5 whorls, of which the 4 outer ones (calyx, corolla, and the 2 whorls of stamens) are most frequently 4 or 5 in number and placed in regular alternation, whilst the innermost one (the carpels) has generally fewer members, probably on account of space (Figs. 360, 361, 421, 429, 487, etc.). Trimerous (Figs. 384, 387, etc.) flowers, or those in which the members of the flower are in threes or a multiple of three, also occur, as well as dimerous flowers; other numbers are rare. It is of the greatest importance in connection with the relative position of the members of the flower to the axis and bract (orientation), whether the bracteoles are typically present (even though they may not be developed), or are typically absent. If there are 2 bracteoles present, then their position in a pentamerous flower is often as follows: the first sepal turns obliquely forward, the second is posterior and median, the third obliquely forward, the fourth and fifth obliquely backward; quincuncial æstivation is often found in these buds (Figs. 360, 429, 471, 475, 584). The first and third leaves, in the following chapters, are most frequently alluded to as the “anterior,” the fourth and fifth as the “lateral” leaves. The _reversed_ arrangement, with the median sepal in the front, occurs for instance in _Papilionaceæ_ (Fig. 511), _Lobeliaceæ_ (Fig. 594), _Rhodoracecæ_. If any bracteoles are present below a tetramerous flower, the relation is generally that 2 sepals (the first ones) stand in the median plane, the two next ones transversely (Fig. 393), and the corolla then adopts a diagonal position (Fig.