Flower

The flower is a highly modified and condensed shoot meant for sexual reproduction. On the basis of its position, a flower may be axillary or terminal. In a typical flower the thalamus consists of four compactly arranged nodes and three highly condensed internodes; from each node of the thalamus a whorl (circle) of modified leaves is produced. A flower may or may not bear a bract at the base of, or along, the pedicel — if it does, it is bracteate, and if not, ebracteate. Similarly, a flower with a pedicel is pedicellate, and one without a pedicel is sessile.

Terminology related to a flower:

• Complete — all four floral whorls are present.
• Incomplete — any one of the floral whorls is absent.
• Perfect — both androecium and gynoecium are present in the flower; also called monoclinous or bisexual.
• Imperfect — only one of the two reproductive whorls is present; also called diclinous or unisexual.
• Unisexual — the flower may be staminate (male) or pistillate (female); also referred to as dicliny.
• Neuter — both reproductive whorls are absent, e.g. the ray florets of Tagetes (marigold).
• Monoecious plant — male and female flowers are borne on the same plant, e.g. Maize.
• Dioecious plant — only one type of unisexual flower is present on a given plant, e.g. Date palm, Papaya. (Some plants, such as Mango, are polygamous — a single plant bears staminate, bisexual and neuter flowers together.)

On the basis of symmetry, a flower that can be cut along only one plane to give mirror-image halves is bilaterally symmetrical and is called zygomorphic, e.g. Sweet pea; a flower that can be cut along any diameter and still give mirror-image halves is radially symmetrical and is called actinomorphic, e.g. Hibiscus.

Insertion of floral whorls. This refers to the position and arrangement of the other floral whorls relative to the gynoecium on the thalamus, and it is decided by the shape of the thalamus:

• Hypogyny — the thalamus is convex or conical, so the ovary occupies the highest position while the other floral parts sit below it. The ovary is said to be superior, and the flower is hypogynous, e.g. Brinjal, Mustard, China rose. It is denoted with the gynoecium symbol G underlined (superior ovary) in the floral formula. …