203. In defining these it will be necessary to use some of the following terms of descriptive botany which relate to inflorescence. If a flower is stalkless, i. e. sits directly in the axil or other support, it is said to be sessile. If raised on a naked stalk of its own (as in Fig. [199]) it is pedunculate, and the stalk is a Peduncle.
[204.] A peduncle on which a flower-cluster is raised is a Common peduncle. That which supports each separate flower of the cluster is a Partial peduncle, and is generally called a Pedicel. The portion of the general stalk along which flowers are disposed is called the Axis of inflorescence, or, when covered with sessile flowers, the Rhachis (back-bone), and sometimes the Receptacle. The leaves of a flower-cluster generally are termed Bracts. But when bracts of different orders are to be distinguished, those on the common peduncle or axis, and which have a flower in their axil, keep the name of bracts; and those on the pedicels or partial flower-stalks, if any, that of Bractlets or Bracteoles. The former is the preferable English name.
Fig. 200. A raceme, with a general peduncle (p), pedicels (p'), bracts (b), and bractlets (b'). Plainly the bracts here answer to the leaves in Fig. [199].
[205.] A Raceme (Fig. [200]) is that form of flower-cluster in which the flowers, each on their own foot-stalk or pedicel, are arranged along the sides of a common stalk or axis of inflorescence; as in the Lily of the Valley, Currant, Barberry, one section of Cherry, etc. Each flower comes from the axil of a small leaf, or bract, which, however, is often so small that it might escape notice, and even sometimes (as in the Mustard Family) disappears altogether. The lowest blossoms of a raceme are of course the oldest, and therefore open first, and the order of blossoming is ascending from the bottom to the top. The summit, never being stopped by a terminal flower, may go on to grow, and often does so (as in the common Shepherd's Purse), producing lateral flowers one after another for many weeks.
Fig. 201. A raceme. 202. A corymb. 203. An umbel.
[206.] A Corymb (Fig. [202]) is the same as a raceme, except that it is flat and broad, either convex, or level-topped. That is, a raceme becomes a corymb by lengthening the lower pedicels while the uppermost remain shorter. The axis of a corymb is short in proportion to the lower pedicels. By extreme shortening of the axis the corymb may be converted into