Daisy Flowers: Daisies are probably the most successful group of plants in the world. Daisy is the accepted common name for members of the Asteraceae family. The old name for this family was Compositae. World wide there are 1100 genera with 25,000 species. In Australia there are 205 native genera with 970 species. As well as these native daisies there are many introduced species that have become weeds and naturalized.
The conventional daisy flower is really an inflorescence known as a capitulum, which is composed of many individual flowers. There are two types of flower. The flowers on the circumference are usually bright and showy and are known as ray florets. These florets are usually sterile and their purpose is to attract pollinators (usually insects). In the centre of each capitulum there is a large number of inconspicuous flowers. These are known as disk florets and are perfect flowers. Disk florets produce seeds. Mature seeds have sepals reduced to bristles, hairs or barbed spines known as pappus. Pappus are the hairy appendages seen on mature daisy flowers such as dandelions. They aid seed dispersal. In this case the seeds are light and are readily dispersed by wind. The seeds of those species with barbed spines are dispersed by hitching a ride in the fur of animals or on human clothing. The efficiency of seed dispersal, by daisies is the major reason for the successful spread of introduced daisies in Australia.
The upper image is a capitulum and the lower is an individual disk flower.