Section A. Structure and Specialized Characters:
VI. Inflorescences

[A. Inflorescence Parts] [B. Inflorescence Types]

A. Inflorescence Parts (Figure 6-4-2)

Bract. Modified, usually reduced, leaf in the inflorescence.
Bracteole or Bractlet. A secondary or smaller bract.
Cupule. Fused involucral bracts subtending flower, as in Quercus.
Epicalyx or Calycle. A whorl of bracts below but resembling a true calyx.
Flower. Modified reproductive shoot of angiosperms.
Involucel. Small involucre; secondary involucre.
Involucre. A group or cluster of bracts subtending an inflorescence.
Pedicel. Individual flower stalk.
Peduncle. Main stalk for entire inflorescence.
Perigynium. Sac-like bract subtending the pistillate flower, as in Carex.
Phyllary. Individual bract within involucre.
Rachilla. Central axis of a grass or sedge spikelet.
Rachis. Major axis within an inflorescence. compound
Ray. Secondary axis in inflorescence.
Scape. Naked peduncle.
Spathe. A sheathing leaf subtending or enclosing an inflorescence.

>a name="b">B. Inflorescence Types (Figure 6-4-2)
(Classification based primarily on arrangement and development)

Note: Inflorescence types are essentially secondary arrangements. The primary arrangement (alternate, opposite, or whorled) of the individual flowers should be indicated; and the tertiary arrangement of sessile-flowered inflorencences should be noted; e.g., spikelets racemose or heads umbellate. See Chapter 27 for structural evolution of inflorescences. Determinate inflorescences have the central flower maturing first with the arrest of the elongation of the central axis; indeterminate inflorescences have the lateral or lower flowers maturing first without the arrest of the elongation of the central axis.

1. Inflorescences with Sessile Flowers

Ament or Catkin. A unisexual spike or elongate axis with simple dichasia that falls as a unit after flowering or fruiting.
Capitulum or Head. A determinate or indeterminate crowded group of sessile or subsessile flowers on a compound receptacle or torus.
Glomerule. An indeterminate dense cluster of sessile or subsessile flowers.
Hypanthodium. An inflorescence with flowers on wall of a concave capitulum, as in Ficus.
Spadix. Unbranched, indeterminate inflorescence with flowers embedded in the rachis.
Spike. Unbranched, indeterminate, elongate inflorescence with sessile flowers.
Spikelet or Locusta. A small spike; the basic inflorescence unit in grasses and sedges.

2. Unbranched Inflorescences with Pedicellate Flowers

Cincinnus. A tight, modified helicoid cyme in which pedicels are short on the developed side.
Corymb. A flat-topped or convex indeterminate cluster of flowers.
Cymule. A simple, small dichasium.
Helicoid Cyme or Bostryx. A determinate inflorescence in which the branches develop on one side only, appearing simple.
Raceme. Unbranched, indeterminate inflorescence with pedicelled flowers.
Scorpioid Cyme or Rhipidium. A zigzag determinate inflorescence with branches developed on opposite sides of the rachis alternately.
Simple Cyme or Dichasium. A determinate, dichotomous inflorescence with the pedicels of equal length.
Umbel. A determinate or indeterminate flat-topped or convex inflorescence with the pedicels arising at a common point.

3. Branched Inflorescences with Pedicellate Flowers

Compound Corymb. A branched corymb.
Compound Cyme. A branched cyme.
Compound Umbel. An umbel with primary rays or peduncles arising at a common point with a secondary umbel arising from the tip of the primary rays; a branched umbel.
Panicle. Branched inflorescence with pedicelled flowers.
Thyrse. A many-flowered inflorencence with an indeterminate central axis and with many opposite lateral dichasia.
Verticillaster. Whorled dichasia at the nodes of an elongate rachis.

4. General Inflorescence Terms and Types

Cyathium. A pseudanthium subtended by an involucre, frequently with petaloid glands, as in Euphorbia.
Monochasium. A cymose inflorescence with one main axis.
Pleiochasium. Compound dichasium in which each cymule has three lateral branches.
Pseudanthium. Several flowers simulating a simple flower but composed of more than a single axis with subsidiary flowers.
Scapose. With a solitary flower on a leafless peduncle or scape, usually arising from a basal rosette.
Secund. One-sided arrangement.
Solitary. One-flowered, not an inflorescence.
Umbellet. The secondary umbel in a compound umbel.