These form the perianth and are in one series, when the flower is termed monochlamydeous, or in two series (dichlamydeous).
When both calyx and corolla are present, the plants are dichlamydeous; when one only is present, the flower is termed monochlamydeous or apetalous, having no petals (fig.
- Monochlamydeous (apetalous) flower of Goosefoot (Chenopodium), consisting of a single perianth (calyx) of five parts, enclosing five stamens, which are opposite the divisions of the perianth, owing to the absence of the petals.
By the suppression of the verticil of the stamens, or of the carpels, flowers become unisexual or diclinous, and by the suppression of one or both of the floral envelopes, monochlamydeous and achlamydeous flowers are produced.
- Tetramerous monochlamydeous male flower of the Nettle (Urtica).