Australian Biological Resources Study
Fern definitions mostly compiled by Mary D.Tindale
(definitions of conifer terms provided by K.D.Hill)
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labium: an outgrowth above the sporangium which partially or wholly covers the ligule.
lacuna: of Isoetes, a cavity within the leaves. pl. lacunae.
laesura: a ridge which surrounds the apertural slit (through which the gemetophyte germinates) in spores of Polypodiophyta; the shape of this ridge reflects the type of spore alignment in the tetrad. pl. laesurae.
lamina: the 'blade' of a frond.
lanuginose: woolly.
leaf gap: a point in the stele at which the vascular supply to a leaf is attached.
leptosporangiate: having sporangia with the walls only one cell thick. cf. eusporangiate.
ligulate: bearing a ligule; strap-shaped.
ligule: a membranous structure towards the base of the upper leaf surface in Isoetes and Selaginella.
lithophytic: growing on rock.
lunate: crescent-shaped.