Solitary flowers or flower-clusters are—
terminal, when borne at the summit of the stem;
axillary, when borne in the axils of the leaves.
A flower-cluster is called—
a raceme, when the flowers are arranged along the axis upon pedicels nearly equal in length;
a corymb, when the flowers are arranged as in the raceme, with the lower pedicels elongated, making the cluster flat-topped;
an umbel, when the pedicels arise from the same point, like the rays of an umbrella, and the cluster is flat-topped;
a panicle, when compound, irregularly made up of a number of racemes;
a spike, when like a raceme, the flowers being without pedicels;
a spadix, when it is a fleshy spike, generally enveloped by a large bract, called a spathe, as in the calla-lily;
an ament, or catkin, when it is a pendent spike, with scaly bracts, like the Willow;
a head, when it is a shortened spike, with a globular form;
a cyme, when it is branched and flat-topped, usually compound, with the older flowers in the center of each simple cluster.
THE INDIVIDUAL FLOWER
A complete flower consists of stamens and pistils (the organs of reproduction), and calyx and corolla (the floral envelops which protect the stamens and pistils). But any one of these organs may be absent.
The calyx is the outer floral envelop, which is more often green, though it is sometimes colored. It may consist of a number of separate parts, called sepals, or these may be more or less united.
The corolla is the inner floral envelop. It is usually colored, and forms the most beautiful feature of the flower, and plays an important part in attracting insects to it, which may carry on the work of fertilization. It may consist of a number of separate parts, called petals, or these may be more or less united, in which case the corolla is said to be gamopetalous. When the calyx and corolla are much alike, and seem like one floral circle, this is referred to as a perianth.
The stamens and pistils are called the essential organs of a flower, because they are necessary to the maturing of the fruit.