TThe so-called complete flowers are carried by the receptacle or more which corresponds to the enlarged end of the floral peduncle. This receptacle usually carries four cycles (whorls) of pieces either from the outside to the inside: • the chalice; • the corolla; • and rosacea; • the gynoecium or pistil.
The chalice is made up of chlorophyllian pieces called sepals.
The androecium is the male part of the flower; it consists of all the stamens.
The latter present a net capped with an expanded mass, Corolla, whose role is to produce the pollen grains.
The gynoecium or pistil is the female part of the flower .
It is formed of the ovary, a closed cavity protecting one or more ovules, and surmounted by a Corolla part, the style, which ends with flowers
n addition to these most frequent elements, we can Corolla, in the nectariferous flowers, nectaries located in a variable zone of the flower, and whose function is to ensure the production of nectar, sweet liquid attracting insects.
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Types of receptacles
There are various types of receptacles, among which are:
• the Corolla type which is characterized by a disc-shaped nectariferous bulge inside the corolla;
inserting floral pieces
According to the mode of insertion of the different floral pieces on the receptacle, one differentiates:
• spiral or acyclic flowers (floral pieces inserted floral pieces the floral axis); • cyclic flowers (floral pieces arranged in successive whorls ); One frequently encounters flowers tetracyclic (four whorls ) and flowers pentacyclic (five whorls ).
Depending on the number of floral parts in a whorl , we distinguish dimers, trimers , tetramers or pentamers ( whorls respectively two, three, four or five floral parts).
These same terms are used to characterize a flower of which all whorls , or at least most, have the same number of pieces.
The relative position of the gynoeceum with respect to thereceptacle makes it possible to differentiate various types of flowers:
• When the gynoecium is inserted on the same plane or slightly higher than the other floral pieces, it is said that the ovary is superior and the insertion of the other floral pieces is hypogynous (Buttercup, Lily …);
• If the center of the receptacle is hollow in the form of a cup, at the same time causing the gynoecium , the ovary is always superior but the insertion of the other floral pieces becomes perigynous ( Rosaceae family );
in these first two cases, the ovary is free compared to other floral pieces.
• The base of the ovary can sometimes penetrate partially into the tissues of the receptacle. The ovary then becomes semi-inferior and the insertion of the other floral pieces is always perigynous ( genus Saxifraga );
• Finally, if the depression of the receptacle is such that the ovary becomes totally trapped by it, by welding their walls, the insertion is epigynous and the ovary inferior. ( Most advanced families such as Orchidaceae, Iridaceae, Apiaceae, Asteraceae and many Rosaceae).
Gender distribution in flowers and between individuals
A flower with both an androcea and a gynoecium is hermaphrodite .
- If it possesses only one or the other, the flower is unisexual :
- A male or staminate flower presents only the
- A female or pistillate flower presents only the
A species is called dioecious if its individuals only have male flowers or female flowers .
The dioecy exists in the willow or the Hops.
A monoecious species carries male and female flowers on the same foot. The monoecy occurs in the Birch, Alder, the Castor …
A polygamous species that presents at the level of the same individual at the same time hermaphroditic flowers and unisexual flowers , male and female ( family Asteraceae).
An actinomorphic or regular flower has an axis of symmetry (symmetry with respect to the center) or several planes of symmetry. This is the case of buttercup.
In all other cases, the flower is irregular and there are still two alternatives:
• The zygomorphic flower has a single plane of symmetry, usually following the anteroposterior plane of the flower . ( family of Lamiaceae or Papilionaceae …); • the asymmetrical flower is devoid of any plane of symmetry. ( family of Valerianaceae …).