Aquatic Plants of Pennsylvania: A Complete Reference Guide

Glossary

Glossary achene—dry, indehiscent, one-seeded fruit with the seed coat not fused to the fruit wall abaxial—the side away from the stem axis acuminate—forming an angle of less than 45 degrees adaxial—the side toward the stem axis adventitious roots—roots that develop at nodes on a stem aerenchyma—spongy tissue in the stems or roots of aquatic plants that allows for buoyancy and gas exchange aereolae—the areas between the veinlets of a leaf alternate-leaved—having only 1 leaf at each node on the stem annual—a plant that completes its entire life cycle in a single growing season anther—sac-like part of the stamen where pollen is produced appressed—flat against a plant organ auriculate—having an ear-shaped appendage awn—a long, bristle-like appendage axil—the junction of leaf and stem axillary—occurring in the leaf axil bract—a small, leaf-like structure, often subtending a flower calyx—collective term for the sepals capillary leaves—very slender, fine, or finely-divided leaves carpel—the organ that bears the ovules and seeds of an angiosperm, the basic unit of the pistil cauline—of the stem ciliate—bearing long, stiff hairs along an edge or keel cleistogamous—flowers that do not open, but undergo self-fertilization and produce seeds compound leaf—a leaf divided into leaflets corm—a vertical, enlarged, solid, underground stem cuticle—natural waxy coating on the surface of leaves and/or stems decumbent—reclining on the surface, but with the tip ascending depauperate—growing in reduced form, often as a result of marginal habitat conditions dichotomous branching—stems repeatedly dividing into 2 equal branches dioecious—species in which male and female flowers are borne on different plants dystrophic—low-nutrient, acidic lakes characterized by peat accumulation and water stained brown by organic acids and tannins emergent—growing with the roots below the water surface, but most of the shoot above the water entire margin—leaf edge that lacks teeth or lobes Block-Rhoads_EM_Final.indd 291 3/21/11 1:27 PM 292 G L O S S A R Y epiphyte—a plant that uses another plant for physical support, but does not derive any nutrition from its host eutrophic—high-nutrient aquatic systems filiform—thread-like frond—a leaf of a fern, also sometimes applied to the segments of duckweed plants glaucous—having a waxy coating, often resulting in a bluish appearance glumes—the pair of bracts at the base of each grass spikelet herbaceous—remaining soft and green during the growing season, not becoming woody imbricate—made up of scales whose edges overlap inferior ovary—condition in which the stamens and perianth are attached above the ovary inflorescence—a grouping or cluster of flowers introduced—a non-native plant that is deliberately brought in to an area invasive species—a species with aggressive growth capable of disrupting normal ecosystem structure or function; many, but not all, invasive species are non-native (exotic) involucre—a set of usually small, overlapping bracts subtending an inflorescence or flower keel—a longitudinal ridge lanceolate—much longer than wide, with the widest part below the middle; lance-shaped lemma—the lower of the 2 bracts that enclose each floret in a grass spikelet ligule—a tongue- or strap-shaped projection present at the junction of the blade and sheath of a grass or sedge leaf mesotrophic—lakes with moderate nutrient levels monoecious—a species with unisexual flowers but with both male and female flowers borne on the same plant mucronate—abruptly tapered to a short, sharp point nerve—a prominent vein in a leaf or other organ node—specific region of a stem at which leaves or buds are produced ocrea—a stipular sheath formed at the nodes of plants in the Smartweed Family ocreolae—a small stipular sheath that subtends flowers or groups of flowers in the Smartweed Family oligotrophic—low-nutrient aquatic systems opposite-leaved—bearing 2 leaves at each node Block-Rhoads_EM_Final.indd 292 3/21/11 1:27 PM G L O S S A R Y 293 ovary—the portion of the pistil that contains the ovules and seeds; the ovary of a flower matures into a fruit palea—the upper of the 2 bracts that enclose each grass flower in a grass spikelet palmate leaf—a compound leaf with the leaflets radiating from a common point of attachment panicle—a branched inflorescence with individually pedicellate...