inflorescence

In plants, a branch, or system of branches, bearing two or more individual flowers. Inflorescences can be divided into two main types: cymose (or definite) and racemose (or indefinite). In a cymose inflorescence, the tip of the main axis produces a single flower and subsequent flowers arise on lower side branches, as in forget-me-not Myosotis and chickweed Stellaria; the oldest flowers are, therefore, found at the tip. A racemose inflorescence has an active growing region at the tip of its main axis, and bears flowers along its length, as in hyacinth Hyacinthus; the oldest flowers are found near the base or, in cases where the inflorescence is flattened, towards the outside. The stalk of the inflorescence is called a peduncle; the stalk of each individual flower is called a pedicel.

Types of racemose inflorescence include the raceme, a spike of similar, stalked flowers, as seen in lupin Lupinus. A corymb, seen in candytuft Iberis amara, is rounded or flat-topped because the pedicels of the flowers vary in length, the outer pedicels being longer than the inner ones. A panicle is a branched inflorescence made up of a number of racemes; such inflorescences are seen in many grasses, for example, the oat Avena. The pedicels of an umbel, seen in members of the carrot family (Umbelliferae), all arise from the same point on the main axis, like the spokes of an umbrella. Other types of racemose inflorescence include the catkin, a pendulous inflorescence, made up of many small stalkless flowers; the spadix, in which tiny flowers are borne on a fleshy axis; and the capitulum, in which the axis is flattened or rounded, bears many small flowers, and is surrounded by large petal-like bracts.