An inflorescence is a cluster of flowers borne on a branch or axis. The arrangement of flowers on the floral axis (peduncle) is called inflorescence. Two major types: Racemose (indefinite): the main axis continues to grow indefinitely, producing flowers laterally in an acropetal order (base to tip). The growing tip is always vegetative (never becomes a flower). Examples: Raceme, Spike, Catkin, Spadix, Corymb, Umbel, Capitulum. Cymose (definite): the main axis terminates in a flower, growth is limited. Younger flowers are at the base, older at the apex (basipetal). Examples: Monochasial cyme, Dichasial cyme, Polychasial cyme. The distinction is fundamental in plant taxonomy and reflects different underlying developmental programs.

Raceme: simple, unbranched axis with pedicellate (stalked) flowers. Example: Mustard (Brassica), Larkspur (Delphinium). Spike: simple, unbranched axis with sessile (unstalked) flowers. Example: Wheat (Triticum), Adhatoda. Catkin (Amentum): spike with small, unisexual flowers. Examples: Mulberry (Morus), Birch. Spadix: fleshy spike with small flowers, enclosed by large bract called spathe. Examples: Maize, banana, Colocasia (arvi). Corymb: flat-topped raceme — pedicles of lower flowers are longer. Examples: Iberis (candytuft), Cauliflower. Umbel: all flowers appear to arise from one point (pedicles of equal length). Simple umbel: Coriander, Carrot (Apiaceae). Compound umbel: multiple umbellets. Capitulum (head): flat/round receptacle bearing sessile florets. Example: Sunflower (Helianthus), Marigold (Tagetes) — Asteraceae family.

In cymose inflorescences, the main axis terminates in a flower → growth is limited (determinate). Younger flowers are at the base (basipetal succession). Monochasial cyme (monopodial): only one daughter branch per node, each ending in a flower. Helicoidal (scorpioid) cyme: branching alternately on opposite sides → curved arrangement. Examples: Heliotropium, Solanum (brinjal). Sympodial: appears like rachis but each 'axis' is the lateral branch. Dichasial cyme (biparous): two daughter branches arise on either side of the terminal flower. Examples: Dianthus, Teak (Tectona). Polychasial cyme: more than two daughter branches. Example: Calotropis (madar/rubber bush).

The capitulum (head) is considered the most evolved/specialised inflorescence. It is characteristic of family Asteraceae (largest family of flowering plants — ~25,000 species). Structure: flat receptacle (thalamus) with two types of florets: Ray florets (ligulate): at periphery, zygomorphic (irregular), often sterile, large and showy petals for attracting pollinators (e.g., white/yellow petals of daisy). Disc florets (tubular): at centre, actinomorphic (regular), fertile, produce seeds. Surrounded by involucre bracts (look like sepals of a single 'flower'). Examples: Sunflower (Helianthus annuus) — seeds in disc, yellow rays for attraction. Marigold (Tagetes). Chrysanthemum. Zinnia. The capitulum looks like a single large flower but is actually many small florets — an example of mass attractant mimicry.

Hypanthodium: a special inflorescence of fig (Ficus). The receptacle becomes hollow and fleshy, enclosing multiple flowers inside. The opening (ostiole) is narrow at the top. Three types of flowers inside: male flowers near top, female flowers (long style) and gall flowers (short style, for wasp breeding) inside. Fig wasp (Blastophaga psenes) pollinates fig through this opening — perfect example of obligate mutualism. Cyathium: inflorescence of Euphorbia (spurge). A cup-shaped (cyathium = cup) structure with: central female flower (reduced to pistil only), surrounding male flowers (each = single stamen), and nectar-secreting glands on the rim. Looks like a single flower — deceptive appearance. Verticillaster: whorled cyme found in Ocimum (basil/tulsi) and other Lamiaceae members — modified dichasial cymes at nodes appear as whorls.

Flower structure is closely tied to pollination mechanism. Wind-pollinated (anemophilous): small, inconspicuous, no petals or reduced petals, no nectar, large amounts of light pollen, feathery stigma. Examples: grasses (Poaceae), Catkins, Maize (corn silk = stigmas). Insect-pollinated (entomophilous): large, colourful, fragrant, produce nectar, sticky pollen. Bee flowers: blue/yellow, landing platform, nectar guides. Butterfly flowers: long narrow tube, red/orange. Moth flowers: white, open at night, strong fragrance. Bird-pollinated (ornithophilous): red/orange, no scent, lots of nectar, robust stamens, anthers positioned to touch bird head. Bat-pollinated (chiropterophilous): large, white, open at night, musty smell, abundant nectar/pollen. Water-pollinated (hydrophilous): rare, aquatic plants (Hydrilla, Vallisneria).

Complete flower: has all 4 floral whorls (calyx, corolla, androecium, gynoecium). Incomplete: missing one or more whorls. Bisexual (hermaphrodite): has both androecium and gynoecium — mustard, lily. Unisexual: staminate (male only) or pistillate (female only) — maize (corn has both on same plant = monoecious), papaya (separate plants = dioecious). Actinomorphic (regular): divisible in multiple planes into equal halves — mustard, chilli. Zygomorphic (irregular): divisible in only one plane — pea (bilateral symmetry). Asymmetric: cannot be divided equally in any plane. Epigynous: stamens appear to grow from top of ovary (inferior ovary) — Asteraceae, Cucurbitaceae, apple. Hypogynous: stamens below ovary (superior ovary) — mustard, brinjal. Perigynous: stamens from rim of cup-shaped thalamus — Rose, Prunus.

Pollination: transfer of pollen from anther to stigma. Self-pollination (autogamy): within same flower. Cross-pollination (allogamy): different plants/flowers. Mechanisms preventing self-pollination: dichogamy (anther and stigma mature at different times — protandry: anther matures first; protogyny: stigma matures first), herkogamy (physical separation of anther and stigma), self-incompatibility (biochemical recognition prevents self-pollen germination), dioecy, monoecy. Double fertilisation (characteristic of angiosperms): one sperm (n) + egg (n) → zygote (2n) → embryo. Second sperm (n) + 2 polar nuclei (n+n = 2n) → primary endosperm nucleus (3n) → endosperm. This double fertilisation is unique to angiosperms — gymnosperms have only single fertilisation. Products: seed = testa (from integuments) + embryo + endosperm. Fruit = ripened ovary wall (pericarp) + seed(s).