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]
- 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.
- 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.
- Central Canal. The large centrally located air space in the stem.
- Carinal Canal. A canal beneath a stem ridge associated with a vascular bundle.
- Vallecular Canal. A canal beneath a stem groove.
- Stele. The central primary vascular system of the stem and associated tissues. Delimited from the cortex by endodermis and pericycle.
- Actinostele. A protostele having a xylem core in the form of radiating ribs, as viewed in transverse section.
- Dictyostele. A dissected solenostele with each individual bundle a meristele.
- Eustele. A dissected siphonostele with phloem only to the outside of the xylem.
- Plectostele. A protostele dissected into anastomosing plate-like units.
- Protostele. Stele having a solid column of vascular tissue with xylem centrally located.
- Siphonostele. A stele having vascular tissue in the form of a hollow cylinder, with a central pith.
- Solenostele. A siphonostele having phloem both internal and external to the xylem.
- Evergreen. Bearing green leaves through the winter.
- Marcescent. The leaves of short duration, dying at the end of the growing season.
(Leaves with a branching vein system which are associated with nodal leaf gap)
- 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.
(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.
- 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.
- False indusium. A folded leaf margin protecting the sorus.
- True indusium. An epidermal outgrowth protecting the sorus.
- Inferior indusium. An indusium attached beneath the sorus with the sporangia appearing above it.
- 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.