Rather than exhaustively reviewing the botanical characters of the inflorescences and flowers of plants in the genus Begonia, I thought it more useful, and less tedious, to describe in detail a few characteristic inflorescences of this vast genus; the specific vocabulary is explained on this first page and illustrated with photos.
Two important remarks :
In the genus Begonia:
- Flower characters play a decisive role in assigning a plant to a section and identifying a species.
- Male and female flowers are always separate.
Vocabulary
Inflorescence
- Axillary inflorescence: an inflorescence arising from the leaf axil.
- Monochasial inflorescence or uniparous cyme: an inflorescence is called monochasial or a uniparous cyme when every axis ends in a single flower.
- Dichasial inflorescence or biparous cyme : an inflorescence in which each axis produces two opposite axes.
- Raceme or Cluster : an inflorescence of stalked flowers attached at different levels, the oldest at the base.
- Few-flowered inflorescence : an inflorescence with few flowers.
- Bisexual inflorescence : the inflorescence has both male and female flowers.
- Unisexual inflorescence : the inflorescence has flowers of only one sex.
- Dioecious plant : male and female flowers are on different plants.
- Monoecious plant : male and female flowers are found on the same plant
- Bracts : modified leaves attached at the base of a peduncle or of one of its branches (when it is branched), which protect the inflorescence before it opens.
- Bracteoles : small bracts on the peduncle between the bracts and the female flowers
Flowers
- Pedicels : the stalks that bear each flower
- Peduncle : the stalk that bears the inflorescence
- Segments or tepals : in the genus Begonia the petals and sepals look alike although they are different, so we use the term segments or tepals (although “tepals” suggests they are identical); they are called outer or inner depending on where they are attached.
- Perianth : all the tepals together.
- Sessile : a flower is sessile when it has no peduncle or pedicel.
- Protandrous : describes a plant whose stamens release pollen before the stigmas are receptive.
- Protogynous : describes a plant whose stigmas are receptive before the stamens release pollen
Male flower
- Stamen / anther / pollen sac / filament / connective : a stamen is the organ of the male flower where pollen is formed; it consists of an anther with locules or pollen sacs containing the pollen, and a filament bearing the anther; the tissue joining the pollen sacs is called the connective.
- Androecium : all the stamens together.
- Actinomorphic : describes the stamens as a whole when they show radial symmetry (about an axis).
- Zygomorphic : describes the stamens as a whole when they are symmetrical about a plane (bilateral symmetry); in this case the stamens usually point in the same direction, like a bunch of bananas
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Female flower
- Pistil: the reproductive organ of the female flower, comprising the ovary and the styles bearing the stigmas.
- Stigmas : the tip of the pistil, which captures pollen (called a stigmatic band when elongated).
- Styles : narrowed parts of the ovary bearing the stigmas.
- Ovary / locules / ovules : the ovary is the hollow part of the female reproductive organ, with several locules containing the ovules; the ovary is topped by the styles.
- Placenta : a thickening of the walls of the ovary’s locules, bearing the ovules (its shape within the locules and the way the ovules are arranged vary).
- Wings : more or less spreading outer appendages of the ovary.
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Miscellaneous
- Apex : tip.
- Apical : located at the tip or top.
- Lanceolate : elongated and pointed, widest towards the base
- Oblanceolate : lanceolate, but widest towards the apex.
- Oblong : clearly longer than wide.
- Obovate : egg-shaped, with the narrowest part at the point of attachment.
- Dehiscence : the opening of an anther or capsule (fruit); also the way these organs open to release pollen or seeds.
- Serrulate : having small teeth, like those of a saw.
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Bibliography
- Studies in Begoniaceae VII / J.JF.E. de Wilde (Wageningen Agricultural University, 1998 / The Netherlands)
- The sections of Begonia / J. Doorenbos – M.S.M. Sosef – J.J.F.E. de Wilde (Backhuys Publishers 2002)
- Dictionnaire illustré de Botanique (Illustrated Dictionary of Botany) / A. Jouy – B. de Foucault (Biotope Editions 2016)
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