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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abaxial: of the side or surface of an organ, facing away from the axis, e.g. the lower or dorsal surface of the lamina. cf. adaxial.
acaulescent: lacking an aerial stem or trunk. cf. caulescent.
acicular: stiff and needle-like.
acrophyll: an adult lamina on the high-climbing portions of some ferns in Lomariopsis and related genera. cf. bathyphyll.
acroscopic: pointing towards the apex. cf. basiscopic.
acrostichoid: with sporangia densely covering the abaxial surface of the lamina, as in Acrostichum.
acuminate: gradually tapering to a protracted point.
acute: terminating in a distinct but not protracted point, the converging edges separated by an angle less than 90°.
adaxial: of the side or surface of an organ, facing towards the axis, e.g. the upper or ventral surface of the lamina. cf. abaxial.
adnate: fused to an organ of a different kind.
aerophore: a localised outgrowth associated with ventilation, as in Cyathea.
alate: winged.
alete: used of a spore which forms alone, i.e. not in diads or tetrads, and hence lacks the laesura characteristic of monolete and trilete spores.
amphistomatic: bearing stomata on both upper and lower lamina surfaces. cf. hypostomatic.
anadromous: a type of venation in which the first set of veins in each segment of the frond originates from the acroscopic side of the midrib, as in Polystichum australiense. cf. catadromous.
anastomosing: of veins, forming a network or reticulum.
anisophyllous: having leaves unequal in size and shape at any one point along a branch. cf. isophyllous.
anisotomous: dichotomies resulting in unequal branching. cf. isotomous.
anisovalvate: when the two valves of a sporangium are unequal in size. cf. isovalvate.
annular: arranged in or forming a ring.
annulus: the elastic ring of cells in a sporangium that initiates dehiscence.
antheridium: the fertile organ of a male gametophyte or the male organ of a bisexual gametophyte, in which the male gametes are formed. pl. antheridia.
antrorse: bent, and pointing towards the apex. cf. retrorse.
apiculus: a small abrupt flexible point at the apex of a pinna or pinnule. adj. apiculate.
apogamous: applied to pteridophytes in which a sporophyte develops from gametophyte cells, other than a fertilised egg.
apogamy: the state of being apogamous.
apomict: a plant that produces viable spores without fertilisation.
appressed: pressed closely against a surface (or another organ) but not united with it.
arachnoid: composed of fine tangled hairs like a cobweb.
arborescent: resembling a tree in height.
archegonium: the structure that produces the female gamete or egg. pl. archegonia.
areole: a space enclosed by the veins of a reticulum.
aristate: having a stiff bristle-like tip.
articulate: jointed; having joints where separation may occur naturally.
asperous: rough to the touch.
attenuate: of pinnae, with sides narrowed concavely to the apex or to the base.
auricle: an ear-like lobe at the base of a lamina, pinna or pinnule. adj. auriculate.