Section A. Structure and Specialized Characters:
VII. Flowers

A. Flower Parts (Figure 6-5-1) (Figure 6-5-2)

Accessory Organs. The calyx and corolla.

Androecium. One or more whorls or groups of stamens; all stamens in flower.

Androgynophore. The stipe or column on which stamens and carpels are borne.

Calyx. The lowermost whorl of modified leaves, sepals.

Carpel. The female sporophyll within flower; floral organ that bears ovules in angiosperms; unit of compound pistil.

Clinanthium. The compound receptacle of the composite head.

Corolla. The whorl of petals located above the sepals.

Disc. A discoid structure developed from receptacle at base of ovary or from stamens around the ovary.

Essential Organs. The androecium and gynoecium.

Gynoecium or Pistil. The whorl or group of carpels in the center or at the top of the flower; all carpels in a flower.

Gynophore. The stipe of a pistil or carpel.

Hypanthium. The fused or coalesced basal portion of floral parts (sepals, petals, stamens) around the ovary.

Pedicel. The flower stalk.

Perianth. An aggregation of tepals or combined calyx and corolla.

Petal. A corolla member or segment; a unit of the corolla.

Polyphore. A receptacle or torus bearing many distinct carpels, as in Rosa.

Receptacle or Torus. The region at end of pedicel or on axis to which flower is attached.

Sepal. A calyx member or segment; a unit of the calyx.

Stamen. The male sporophyll within the flower; the floral organ that bears pollen in angiosperms.

Tepal. A perianth member or segment; term used for perianth parts undifferentiated into distinctive sepals and petals.

Whorl. A cyclic or acyclic group of sepals, or petals, or stamens, or carpels.

B. Flower Types (Figure 6-6-1)
(Classification based on evolutionary flower-pollinator relationships--from Leppik [1957])

Actinomorphic. Flowers with radial symmetry and parts arranged at one level; with definite numbers of parts and size; e.g., Anemone, Caltha.

Amorphic or Paleomorphic. Flowers without symmetry; usually with an indefinite number of stamens and carpels, and usually subtended by bracts or discolored upper leaves; e.g., Salix discolor, Echinops ritro. (mostly fossil forms).

Haplomorphic. Flowers with parts spirally arranged at a simple level in a semispheric or hemispheric form; petals or tepals colored; parts numerous; e.g., Nymphaea, Magnolia.

Pleomorphic. Actinomorphic with numbers of parts reduced; e.g., Tripogandra.

Stereomorphic. Flowers 3-dimensional with basically radial symmetry; parts many or reduced, and usually regular; e.g., Narcissus, Aquilegia.

Zygomorphic. Flowers with bilateral symmetry; parts usually reduced in number and irregular; e.g., Cypripedium, Salvia.