Fig. 214.—Lateral Racemes (in fruit) of Barberry.
A very short and dense spike is a head. Clover (Fig. [216]) is a good example. The sunflower and related plants bear many small flowers in a very dense and often flat head. Note that in the sunflower (Fig. [189]) the outside or exterior flowers open first. Another special form of spike is the catkin, which usually has scaly bracts, the whole cluster being deciduous after flowering or fruiting, and the flowers (in typical cases) having only stamens or pistils. Examples are the “pussies” of willows (Fig. [182]) and flower-clusters of oak (Fig. [180]), walnuts (Fig.[ 204]), poplars.
Fig. 216.—Head of Clover Blossoms.
Fig. 217.—Corymb of Candy-tuft.
When a loose, elongated centripetal flower-cluster has some primary branches simple, and others irregularly branched, it is called a panicle. It is a branching raceme. Because of the earlier growth of the lower branches, the panicle is usually broadest at the base or conical in outline. True panicles are not very common.
When an indeterminate flower-cluster is short, so that the top is convex or flat, it is a corymb (Fig. [217]). The outermost flowers open first. Centripetal flower-clusters are sometimes said to be corymbose in mode.
When the branches of an indeterminate cluster arise from a common point, like the frame of an umbrella, the cluster is an umbel (Fig. [218]). Typical umbels occur in carrot, parsnip, caraway, and other plants of the parsley family: the family is known as the Umbelliferæ, or umbel-bearing family. In the carrot and many other Umbelliferæ, there are small or secondary umbels, called umbellets, at the end of each of the main branches. (In the centre of the wild carrot umbel one often finds a single, blackish, often aborted flower, comprising a 1-flowered umbellet.)
