Glossary of botanical terms used in the Poaceae

aristate - with an awn

aristulate - diminutive of aristate

auricle - an earlike lobe or appendage at the junction of leaf sheath and blade

auriculate - with an auricle

awn - a bristle arising from a spikelet part

callus - a hard projection at the base of a floret, spikelet, or inflorescence segment, indicating a disarticulation point

caryopsis - a specialized dry fruit characteristic of grasses, in which the seed and ovary wall have become united

collar - pale or purplish zone at the junction of leaf sheath and blade

column - the lower twisted portion of a geniculate awn, or the part below the awn branching-point in Aristideae

compound - referring to inflorescences made up of a number of small constituent inflorescences (as in some Andropogoneae), or a raceme with some secondary branching

culm - the flowering stem of a grass plant

culm sheath (bamboos) - modified, often non-photosynthetic, culm leaf with an expanded sheath and much reduced blade, usually deciduous as the culm matures

diffuse (bamboos) - culms arising singly from long slender rhizomes.

extravaginal - branching in which the young shoot breaks through the base of the leaf sheath

floret - the individual unit of a spikelet, comprising a lemma and palea with enclosed reproductive organs

glume - one of a pair of empty scales at the base of a grass spikelet

heterogamous spikelets - the paired spikelets found in most Andropogoneae, where one spikelet of the pair is sessile and produces a caryopsis, and the other spikelet is pedicelled, of different form, and staminate or sterile

hilum - the scar on the caryopsis marking the site of the attachment of the pericarp and testa, found on the opposite side from the embryo

homogamous spikelets - in Andropogoneae the paired spikelets sometimes present at the base of the raceme, of similar appearance and not producing any caryopses, often resembling the pedicelled spikelets or assuming a protective involucral function

intravaginal - branching in which the young shoot grows up inside the leaf sheath, emerging at the sheath mouth

iterauctant (bamboos) - inflorescence with pseudospikelets with glumes subtending axillary buds capable of partial or extensive spikelet ramification

leaf blade - the distal expanded part of a grass leaf

leaf sheath - the basal part of the grass leaf which normally encloses a culm internode

lemma - the lower of the two bracts enclosing the grass flower and together with the palea comprising a floret

leptomorph (bamboos) - rhizome monopodial, elongated, more slender than culms

ligule - a membrane or line of hairs on the inner (adaxial) side of the junction of the leaf sheath and leaf blade; bamboos sometimes have an external ligule on the abaxial side of the junction

lodicule - a small scale-like or fleshy structure at the base of the stamens in a grass floret, usually 2 in each floret (often 3 or more in bamboos); they swell at anthesis, causing the floret to gape open

oral setae - marginal setae inserted at junction of leaf sheath and blade, on the auricles when these are present

pachymorph (bamboos) - rhizome sympodial, thicker than culms

palea - the upper and inner scale of the grass floret which encloses the grass flower, usually 2-keeled

panicle - in grasses, an inflorescence in which the primary axis bears branched secondary axes with pedicellate spikelets

pedicel - in grasses, the stalk of a single spikelet within an inflorescence

peduncle - the stalk of a raceme or cluster of spikelets

pluricaespitose (bamboos) - culms arising in a series of clusters along a long slender rhizome

prophyll - in grasses, a 2-keeled, hyaline, modified leaf, placed within a leaf sheath on the adaxial side of a branch

pseudopetiole - the narrow basal portion of some leaf blades, resembling a petiole

pseudospikelet (bamboos) - spikelet in which the outer glumes or bracts subtend axillary buds which can develop to form lateral spikelets or branches

raceme - in grasses, an unbranched axis bearing spikelets; racemes may be solitary, digitate, or scattered

raceme base - short stalk beneath the individual racemes of a pair in some Andropogoneae

raceme pair - pairs of racemes supported by spatheoles in the compound panicles of some Andropogoneae

rachilla - the central axis of the spikelet which bears the florets

rachilla extension - a prolongation of the rachilla beyond the uppermost (or single) floret

rachis - the axis of a raceme

secondary spathe - spathe supporting a second tier of branching within the compound panicle of some Andropogoneae

semelauctant (bamboos) - inflorescence with glumes not subtending viable buds or branches

sinus - the space between two projecting lobes or teeth

spathate - with spathes

spathe - a bract or modified bladeless leaf subtending the inflorescence or part of it

spatheole - the uppermost spathe supporting the racemes within the compound inflorescence of some Andropogoneae

spikelet - the basic unit of a grass inflorescence; usually composed of two glumes and one or more florets on a rachilla

spikelet pair - the arrangement of one sessile and one pedicelled spikelet arising from the same node characteristic of the Andropogoneae

tiller - a leafy non-flowering shoot

triad - a group of three spikelets borne together

unicaespitose (bamboos) - culms all arising in a single clump from pachymorph rhizomes