Examples of species with spiral flowers are Magnolia grandiflora (magnoliaceae), Victoria cruziana (nymphaeaceae) and Opuntia ficus-indica (cactaceae).
The flowers called actinomorphics, radiate or polysymmetric have radial symmetry, as is the case of Tulipa gesneriana (liliaceae) or Linum usitatissimum (linaceae).
[8] In the perianth flowers may be the case that only present calyx, so they are called monoclamyds or, more usually, apetalous and the most conspicuous example is the urticaceae family.
The vexillary vernation is a variant of the preceding one, with the totally internal piece contiguous to the external one, which occupies a superior position.
Depending on its duration with respect to the other floral parts, the calyx may be ephemeral or fleeting, when the sepals fall when the flower opens, as in the poppy (Papaver rhoeas, Papaveraceae); deciduous, when the sepals are shed after fertilization has occurred; or persistent when it remains after fertilization and accompanies the fruit, as in the apple tree (Malus domestica, rosaceae).
In other species as for example in Impatiens balsamina, some of the calyx pieces acquire the shape and coloration of petals and, for that reason, they are adjectivized as petaloids.
[1] In certain genera—Narcissus, for example—at the top of the claw there is a ligular appendage that forms a cup inside the tepal cycle called paraperigonium or "false corolla".
[14] The shape of the gamopetalous corolla can be very varied: tubulose (cylinder-shaped, as in the central flowers of the capitula of the compositae family), infundibuliform (funnel-shaped, as in sweet potato, Ipomoea batatas, convolvulaceae); bell-shaped (like an inflated, bell-like tube, as in thrush, Convallaria majalis, ruscaceae), hypocrateriform (shaped like a long, slender tube, as in Jasminum), labiated (with the blade formed by two unequal segments, as in Salvia splendens, a lamiaceae), ligulated (with the tongue-shaped blade, which is seen in the peripheral flowers of the capitula of many compositae) and spurred (when it has one or more nectariferous spurs, as in Aquilegia).
In many petals, such as those of Brassica napus, the papillae are conical, with a marked cuticular thickening at the apex, and radial striations toward the base.
It has been suggested that these thickenings allow an even diffusion of the emerging light, so that the brightness of the petals is uniform at any angle of illumination.
The petals may have air spaces in subepidermal position or a layer of cells with abundant starch grains, and in both cases the light is reflected.
[16] In some species the basal parts of the petals contain a flavonolglucoside called chalcone, which absorbs ultraviolet light, turning them into "nectar guides" for pollinating insects.
If the opening occurs along the entire length of the septum separating the pollen sacs, the dehiscence is longitudinal, which is the most frequent case.
This type of flowers is usually arranged in inflorescences that, because of their shape, look like brushes or pipe cleaners, as for example in the leguminous plants Inga uruguensis and Acacia caven and in the myrtaceae such as Callistemon rigidus.
[8] The style is variable in length, from less than 0.5 mm (subsessile stigma) to more than 30 cm in certain varieties of maize, which is known as corn silk.
[26] Moist stigmas release an exudate during the receptive period and occur in families such as orchidaceae, scrophulariaceae and solanaceae.
They can be feathery (grasses) or non-feathery and, in this case, papillose (Cordyline, Yucca Pelargonium or non-papillose (Asclepias, Capparis, Cyperus]).
There are different types of placentation: Floral sexuality is related to the presence or absence of the reproductive whorls: androecium and gynoecium.
In many other species, on the other hand, the flowers have only one reproductive whorl and are said to be diclinate, imperfect or unisexual, as is the case in mulberry (Morus nigra, moraceae) and pumpkin (Cucurbita maxima, cucurbitaceae).
Such flowers, called neutral or asexual, are usually arranged on the periphery of the inflorescence and can be observed, for example, in many species of the compositae family, such as the daisy (Bellis perennis) or sunflower (Helianthus annuus).
By means of these diagrams the floral structure is well manifested, its symmetry is deduced from it, the number of members of each whorl, and in the case of the sepals and petals, their vernation, their welding or independence; of the androecium the relative position of the stamens with respect to the perianth, the concrescence or separation of the same, their union or autonomy with respect to the corolla and the introrse or extrorse position of the anthers.
The flowers are hermaphrodites, actinomorphics (i.e., of radial symmetry) or slightly zygomorphics, pedicellate or sessiles, showy, each associated with a filiform bract.
The tepals are free from each other or may be welded at the base forming a perigonial tube or hypanthium, which is extended in some cases in a "crown"—also called paraperigonium or false corolla, for example in Narcissus—sometimes reduced to scales or unremarkable teeth.
The filaments are slender, filiform or flared at the base, may be free (Hippeastrum) or bound together by a membrane surrounding the entire ovary called the "staminal cup", as for example in Hymenocallis.
[32][33] In compositae, the sunflower family and margarita, the flowers are small, hermaphrodites or, sometimes, functionally unisexuals or sterile (in the latter case they are called neutral).
The calyx is null or the sepals are deeply modified, forming a pappus, from two to many scales, bristles or hairs, persistent, sometimes joined.
[34] Leguminosae, the acacias and bean family, have a great diversity of flower types, depending on the subfamily considered, mimosoideae, caesalpinioideae and faboideae.
The corolla is composed of 5 free petals (commonly less than 5 or absent in Swartzieae, Amorphieae and Caesalpinioideae, or 3 to 4 in Mimosoideae) or partially united and presents, in general, a characteristic morphology.
These lodicules are the organs that, when they become turgid, determine the opening of the antecio or floral box during flowering, allowing the feathery stigmas and the stamens to be exposed.
The androcecium is fused to the style and stigma, which are highly modified, forming a structure known as a column, gynostema or gynostegium.