It is the mode of arrangement of flower in a group in a specialized branch called peduncle. It consists of inflorescence axis and mother axis. Peduncles are of two types- receptacle and scape.
Different types of inflorescence that are observed are:
1. Racemose inflorescence - It is of two types.
Simple racemose inflorescence:
Typical Raceme - Unbranched, elongated peduncle bearing pedicellate or stalked flowers acropetally. Example - Delphinium, Linaria etc.
Corymb - All the acropetally arranged flowers come to lie at the same level due to slight shortening or elongation of peduncles of lower flowers. Example- candytuft.
Corymbose raceme - Like a corymb near the growing point and raceme lower down though the peduncles of the lower flower are longer. Example - mustard.
Umbel - Pedicellate flowersarranged centripetally around an extremely reduced peduncle with an involucre below. Example - Brahmi booti, hydrocotyle.
Spike - Sessile flowers borne acropetally over an elongated peduncle. Example –bottle brush, Amaranthus.
Spikelets - It is a compact spike having a few flowers born on axis called rachilla and surrounded by two scales called glumes. Example- wheat, oat, grass etc.
Strobile - It is a spike in which the flowers develop in the axils of persistent membranous bracts. Example- Hop.
Catkin - Compact unisexual spike often hanging. Example-Mulberry, Willow,Birch.
Spadix - It is a modification of catkin in which the peduncle is fleshy and thick with upper part sterile and lower part bearing one or both the types of unisexual flowers surrounded by a large bract called spathe. Example-In maize the female flower develops in a spadix.
Capitulum - Peduncle is flattened to form receptacle that bears the centripetally arranged Sessile flowers or florets surrounded by involucre of bracts. Example- Cosmos, Zinnia, Chrysanthemum etc.
Compound racemose inflorescence:
Raceme of racemes - Racemes are born acropetally on a raceme. Example - yucca, Asparagus etc.
Corymb of corymbs – An axis bearinga number of corymbs in a corymbose fashion. Example - Cauliflower, Pyrus.
Umbel of umbels - Many umbels develops from a common point in an umbellate fashion. Example - coriander, carrot, cumin.
Spike of spikes - Example - Amaranthas
Spike of spikelets - Example - Wheat.
Spadix of spadices - Example – Date pulm, Coconut.
Capitulum of capitula - Echinops.
2. Cymose Inflorescence:
Uniparous – Example – Begonia, Drosera.
Biparous – Example - Dianthus, Nyctanthes.
Multiparous –Calotropis, Hamelia.
Cymose head – Kadam, Acacia.
Scapigerous – Onion.
3. Mixed inflorescence - They are of different types –
Thyrsus – Cymose cluster arranged acropetally. Example - grape vine.
Mixed spadix – Spadices have cymose inflorescence arranged acropetally on fleshy axis. Example - Banana.
Panicle of spikelets – Spikelets arranged in a compound raceme. Example- oat, rice.
Corymb of capitula – Example- Ageratum.
Other types – Like umbel of capitula, cyme of umbels . Example- Lantana.
Special inflorescence: - They are of four types:
Hypanthodium – It is flask shaped fleshy (male flowers),a pore or ostiole lined by scales and a short canal bearing hair. Example- peepal, banyan.
Coenanthium – Saucer shaped receptacle with upturn margin bearing florets. Example-Dorstenia .
Verticillaster – It is raceme of verticles or whorls of flowers born in the axile of opposite leaves . Example- Ocimum, salvia.
Cyanthium – Consists of involucre of 5 fused bracts that encloses a central achlamydeous pedicellate tricarpellary,syncarpous female. Example-Euphorbia.