Editing Asteraceae (section)

=== Floral structures<span class="anchor" id="Floral structures"></span> ===
[[File:Carduus floral diagram.svg|thumb|Flower diagram of ''[[Carduus]]'' (Carduoideae) shows (outermost to innermost): subtending bract and stem axis; calyx forming a pappus; fused corolla; stamens fused to corolla; gynoecium with two carpels and one [[locule]]]]
[[File:Senecio mikanioides (delairea odorata).jpg|thumb|Discoid flowerheads of ''[[Delairea odorata]]''.]]
The distinguishing characteristic of Asteraceae is their [[inflorescence]], a type of specialised, composite flower head or ''[[pseudanthium]]'', technically called a calathium or ''[[Pseudanthium|capitulum]]'',<ref name=Beentje/><ref name=Usher/> that may look superficially like a single flower. The ''capitulum'' is a contracted [[raceme]] composed of numerous individual [[Sessility (botany)|sessile]] flowers, called ''florets'', all sharing the same [[Receptacle (botany)|receptacle]].

A set of [[bract]]s forms an [[involucral bract|involucre]] surrounding the base of the capitulum. These are called "phyllaries", or "involucral bracts". They may simulate the sepals of the pseudanthium. These are mostly herbaceous but can also be brightly coloured (e.g. ''[[Helichrysum]]'') or have a scarious (dry and membranous) texture. The phyllaries can be free or fused, and arranged in one to many rows, overlapping like the tiles of a roof (''imbricate'') or not (this variation is important in identification of tribes and genera).

Each floret may be subtended by a bract, called a "palea" or "receptacular bract". These bracts are often called "[[chaff]]". The presence or absence of these bracts, their distribution on the receptacle, and their size and shape are all important diagnostic characteristics for genera and tribes.

The florets have five petals fused at the base to form a [[Corolla (flower)|corolla]] tube and they may be either [[actinomorphic]] or [[zygomorphic]]. ''Disc florets'' are usually actinomorphic, with five petal lips on the rim of the corolla tube. The petal lips may be either very short, or long, in which case they form deeply lobed petals. The latter is the only kind of floret in the [[Carduoideae]], while the first kind is more widespread. ''Ray florets'' are always highly zygomorphic and are characterised by the presence of a ''ligule'', a strap-shaped structure on the edge of the corolla tube consisting of fused petals. In the Asteroideae and other minor subfamilies these are usually borne only on florets at the circumference of the capitulum and have a 3+2 scheme – above the fused corolla tube, three very long fused petals form the ligule, with the other two petals being inconspicuously small. The Cichorioideae has only ray florets, with a 5+0 scheme – all five petals form the ligule. A 4+1 scheme is found in the Barnadesioideae. The tip of the ligule is often divided into teeth, each one representing a petal. Some marginal florets may have no petals at all (filiform floret).

The calyx of the florets may be absent, but when present is always modified into a [[Pappus (botany)|pappus]] of two or more teeth, scales or bristles and this is often involved in the dispersion of the seeds. As with the bracts, the nature of the pappus is an important diagnostic feature.

There are usually four or five [[stamen]]s.<ref name=Spellenberg2001 /> The filaments are fused to the corolla, while the anthers are generally [[connation|connate]] (''syngenesious'' anthers), thus forming a sort of tube around the style (''theca''). They commonly have basal and/or apical appendages. Pollen is released inside the tube and is collected around the growing style, and then, as the style elongates, is pushed out of the tube (''nüdelspritze'').

The [[pistil]] consists of two connate [[carpel]]s. The [[carpel|style]] has two lobes. Stigmatic tissue may be located in the interior surface or form two lateral lines. The [[ovary (plants)|ovary]] is inferior and has only one [[ovule]], with basal [[placentation]].