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The perianth is the flower structure comprising the two sterile whorls, the calyx and the corolla. In many cases, as for example in weeping willow ( Salix babylonica , salicaceae ) or European ash ( Fraxinus excelsior , oleaceae ) the perianth may be missing, that is, the flowers have only the fertile whorls (androecium and gynoecium) and are ...
A floral diagram is a graphic representation of the structure of a flower. It shows the number of floral organs, their arrangement and fusion. Different parts of the flower are represented by their respective symbols. Floral diagrams are useful for flower identification or can help in understanding angiosperm evolution.
Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirally arranged.
The morphology of a flower, or its form and structure, [10] can be considered in two parts: the vegetative part, consisting of non-reproductive structures such as petals; and the reproductive or sexual parts. A stereotypical flower is made up of four kinds of structures arranged in whorls around the tip of a short stalk or axis, called a ...
Symmetry or arrangement may be described for the whole flower; in such case the corresponding symbol is usually placed at the beginning of the formula. It may be also outlined separately for different organs, placing it after their labels or numbers, or it may not be included in the formula at all. It is described by following symbols:
For example, a double raceme is a raceme in which the single flowers are replaced by other simple racemes; the same structure can be repeated to form triple or more complex structures. Compound raceme inflorescences can either end with a final raceme (homoeothetic), or not (heterothetic). A compound raceme is often called a panicle.
For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts. The homology of leaves is an easy conclusion to make. The plant morphologist goes further, and discovers that the spines of cactus also share the same basic structure and development as leaves in other plants ...
Actinomorphic – having a radial symmetry, as in regular flowers. Actinomorphy – when the flower parts are arranged with radial symmetry. Radial – symmetric when bisected through any angle (circular) Unisexual – Zygomorphic – one axis of symmetry running down the middle of the flower so the right and left halves reflect each other.