Section D. Lower Vascular Plant Glossary

(Contributed by John T. Mickel, New York Botanical Garden.)

[I. Sporophyte:  IA. Stems - IB. Leaves - IC. Reproductive Structures] [II. Gametophyte] [III. Asexual Reproduction]


A. Stems

1. Branching

Axial. With branches arising from buds in leaf axil.
Dichotomous. With branches forking into two more or less equal parts.
Epipetiolar. With branches arising from buds on the petiole.
Monopodial. Having one main axis of growth.
Random. With branches arising from buds without relation to leaves.
Sympodial. With branches more or less equal without a main axis.

2. Phyllotaxis

Distichous. With leaves in two rows.
Polystichous. With leaves in several rows.

3. External Features

Aerial Stem. An erect stem arising from a horizontal rhizome.
Articulate. Generally meaning having a joint as in leaves, leaflets or stems, as in heterophyllous species of Selaginella; or having a swollen area, often discolored, at the point of branching of the stem.
Jointed. With stems that can be pulled apart easily at the nodes, as in Equisetum.
Node. Point on the stem where leaves are attached; or the point of branching of the stem.
Rameal Sheath. Leaf sheath on the stem joints, as in Equisetum.
Tubercules. Silica deposits on the stem ridges, as in Equisetum.

4. Internal Features

Canals. As in Equisetum.
Stele. The central primary vascular system of the stem and associated tissues. Delimited from the cortex by endodermis and pericycle.

B. Leaves

1. Duration

Evergreen. Bearing green leaves through the winter.
Marcescent. The leaves of short duration, dying at the end of the growing season.

2. Megaphylls
(Leaves with a branching vein system which are associated with nodal leaf gap)

a. General

Crozier. The coiled developing leaf of a fern.
Frond. The leaf of a fern.

b. Parts of a Leaf

Blade. The expanded portion of a leaf.
Costa. The midvein of a minor divsion of a fern leaf.
Lamina. The leaf tissue other than the veins or axes.
Pinna. A primary division of a fern leaf.
Pinnule. A secondary division of a fern leaf.
Rachis. The axis of a compound fern blade.
Segment. The ultimate division or unit of a dissected fern leaf.
Stipe. The petiole of a fern leaf.
Stipe Bundles. The vascular bundles of the fern petiole.

c. Venation Patterns

Areoles. The spaces formed by a vein network.
False Veins. Small vein-like areas of thick-walled cells in the leaves of some lower vascular plants.
Free. No veins uniting to form a network.
Included Veinlets. Veins ending inside areoles.
Net. Veins uniting to form a network.

d. Leaf Division

Bipinnate. Twice pinnate.
Pectinate. Pinnatifid with closely set segments; comb-like.
Pinnate. Compound, with the leaflets arranged on both sides of a common axis.
Pinnate-pinnatifid. Pinnate with pinnatifid pinnae.
Pinnatifid. Pinnately cut, more than half way to the midvein
Simple. Undivided.

e. Blade Architecture

Anadromous. Having the first lobe or segment of a pinna arising basiscopically in compound leaves.
Catadromous. Having the first lobe or segment of a pinna arising acroscopically in compound leaves.
Imparipinnate. Pinnate with a conform terminal leaflet.
Palmate. Radiately lobed or divided.
Pedate. Palmately cut or divided with the lower pair basiscopically exaggerated.
Pinnate. Compound, with the leaflets arranged on both sides of a common axis.

f. Dimorphism (Figure 6-18-2)
(With leaves of two types in ferns, the fertile being of different size, shape or dissection than the vegetative)

Complete Dimorphism. Leaves completely fertile or vegetative.
Partial Dimorphism. Leaves with only a part modified as fertile sporangia.
Slight Dimorphism. Fertile and vegetative leaves only slightly different in appearance.
Vegetative Frond. Frond lacking sporangia.

3. Microphylls
(Leaves with only one vein and no leaf gap.)

Axillary leaves. Leaves borne in the axils of branches, as in heterosporous species of Selaginella.
Bast bundles (peripheral strands). Bundles of thick-walled cells parallel to the midrib, as in Isoetes.
Lacuna. Chamber or internal air space.
Lateral leaf. Leaf on the side of the stem, as in heterophyllous species of Selaginella.
Ligule. A small membranous outgrowth or projection at the base of the leaf, appearing above the sporangium in fertile leaves, as in Selaginella and Isoetes.
Median leaf. Leaf on top of stem, as in heterophyllous species of Selaginella.
Seta. A hair-like extension of the leaf, as in homophyllous species of Selaginella.

C. Reproductive Structures (Figure 6-18-4)

Annulus. Thick-walled ring of cells on the sporangium.
Elater. One of four elongate appendages on the spores, as in Equisetum.
Eusporangiate. Having the sporangium develop from a great amount of leaf tissue as opposed to only one or a few cells.
Exospore or Exine. Outer spore wall layer.
Fovea. Pit or depression containing the sporangium in the leaf base of Isoetes.
Heterosporous. Having two kinds of spores, usually differing in size.
Homosporous. Having spores of only one kind.
Indusium. A flap of tissue covering a sorus.
Leptosporangiate. Having the entire sporangium develop from a periclinal division of a superficial cell or small group of cells.
Lip Cells. The line of cells between which the sporangium dehisces.
Massula. A clump of microspores, as in Azolla.
Megasporangium. The sporangium in which megaspores are produced.
Megaspore. A spore that gives rise to a female gametophyte.
Megasporophyll. A leaf bearing one or more megasporangia.
Microsporangium. The sporangium in which microspores are produced.
Microspore. A spore that gives rise to a male gametophyte.
Microsporophyll. A leaf bearing one or more microsporangia.
Paraphyses. Hairs or hair-like structures in the sorus
Perispore or Perine. An outer covering of some fern spores, with different configuration than that of the exospore.
Receptacle. Point on a leaf where sporangia are attached.
Sorus. A cluster of sporangia.
Sporangiophore. The umbrella-shaped sporangium-bearing unit of the strobilus, as in Equisetum.
Sporangium. A spore case.
Spore Shapes. Monolete. Bean-shaped, with a single scar line.
Trilete. Basically tetrahedral, but often appearing round or triangular, with three scar lines forming a Y.
Sporocarp. A hard, nut-like structure containing the sporangia in heterosporous ferns.
Sporophyll. A leaf bearing sporangia.
Stomium. Lip cell region of a fern sporangium.
Strobilus. Stem with short internodes and spore-bearing appendages; a cone.
Velum. The membranous flap covering the sporangium, as in Isoetes.


Antheridium. The male sex organ producing the sperm.
Archegonium. The female sex organ producing the egg.
Prothallus. Gametophyte of lower vascular plants.
Rhizoid. A hair-like absorptive organ on gametophytes and rarely on sporophytes.


Apogamy. Producing sporophytes from a gametophyte without fertilization.
Apospory. Producing gametophytes directly from a sporophyte without producing spores.
Bulblet. A small, bud-like vegetative propagule produced on the leaves of some ferns.
Gemma. A vegetative reproductive bud borne on the stem, as in Lycopodium; a multicellular reproductive propagule on gametophytes, as in ferns.