Glossary - general

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Water stoma – an epidermal pore without guard cells, which is present on the surface or margin of a leaf and exudes water

Wax – substance which consists of saturated and unsaturated hydrocarbons, also some substation by oxygen, i.e. fatty acids esterified with long-chain alcohols

Weakly crassinucellar ovule – pseudotenuinucellar ovule; the parietal cell does not divide again or only once and may disappear, the ovule then appearing as if tenuinucellar; with a megasporangium in which the meiocyte is covered at the apex by only one subepidermal layer in addition to the epidermis – see also Crassinucellar ovule and Tenuinucellar ovule

Wet type stigma – receptive surface having a free-flowing secretion when in the receptive state; frequent in species with binucleate (bicellular) pollen grains

Whippy – long, thin and bendy

Whorl – verticil; a set of similar organs arranged in a circle around a central axis

Whorled – arranged in a circle around a central axis (e.g. leaves around a stem)

Wide-band tracheid (WBT) – short barrel-shaped tracheids with wide helical or annular thickenings projecting into the cell lumen; a type of tracheid, in which the cell wall thickenings are tall and partially occluding the lumen

Wing – (1) (Faboideae) ala; lateral petal of a papilionoid flower; (2) a flattened extension to any organ

Wing bundles – lateral subsidiary vascular bundles present in the petioles in some angiosperms

Winged (of a three dimensional body) – with flattened to blade-like ridges on either side

Winged-aliform axial parenchyma – parenchyma cells surrounding or to one side of the vessel and with lateral extensions being elongated and narrow

Withered (of non-woody plant parts) – dried out

Withering – diminishing in volume and becoming brown and wrinkled while dying

Wood – lignified xylar tissue of shrubs and trees; secondary xylem tissue

Wood fibres – xylem fibres; fibre tracheids and libriform fibres present in the xylem (wood); morphologically intergrading with imperforate tracheary elements and parenchyma cells

Wood ray – a vertically elongated band of often radially elongated parenchtymatous cells traversing the conducting elements (in xylem and phloem)

Woody – wood-like (more or less lignified) tissue