Figure 28.10 Inflorescences (A) The inflorescence of the giant hogweed, a member of the carrot family, is a compound umbel. Each umbel bears flowers on stalks that arise from a common center. (B) Zinnias are members of the aster family; their inflorescence is a head. Within the head, each of the long, petal-like structures is a ray flower; the central portion of the head consists of dozens to hundreds of disc flowers. (C) Some grasses, such as Johnson grass, have inflorescences called spikes, which are composed of many smaller groups of flowers, or spikelets.