A flower is a highly modified stem specialized for reproduction. The modified leaves that form the flower parts are called anthophylls. The modified stem is called a peduncle if the flower is solitary and a pedicel if the flower is part of an inflorescence. The end of the modified stem into which the anthophylls are inserted is called the receptacle or floral thalamus. Four types of anthophylls are found in a typical, complete flower: the sepals, petals, stamens and carpels or pistil, all in varying numbers depending on the species.
The floral peduncle is a portion of the stem like a more or less developed cylindrical axis that supports the flower. The upper part of the peduncle where the other parts of the flower are inserted are called: Thalamus, Floral Shaft or Receptacle that is often somewhat widened, very short and takes shape: Discoidal, cylindrical, convex, flattened, concave or deeply excavated in such a way that the floral parts arranged in whorls or cycles are close to each other.
The floral sheaths are constituted by a set of accessory parts that surround or protect the essential or sexual organs, their constitution and nature is very varied. The floral envelopes are formed by two whorls: a) CALYX: it is the set of sepals b) COROLLA: it is the set of petals.
The sexual organs form the innermost whorls of the flower, i.e. the 3rd, 4th and 5th whorl. They are formed, like the sepals and petals, by modified leaves. The sexual organs can never be absent since they constitute the flower itself. These are: a) Androceo – male sexual organ b) Gynoecium – female sexual organ.
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