An On-line Version of an Aquatic Plant Identification Manual for Washington's Freshwater Plants


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Achene: A hard, dry, one-seeded fruit that does not split open when mature. Often looks like a seed. Achene line drawing 
Alkaline: Containing soluble mineral salts (alkaline waters are considered to be hard water). 
Alternate: A leaf arrangement where each leaf occurs singly at each node. See line drawing
Annual: A plant that completes its life cycle and dies within one year (such as petunias). 
Anther: A male flower part. The pollen bearing structure at the top of the stamen. See line drawing of flower parts
Beak: A hardened projection often seen on the edge of pondweed achenes. 
Blade: The broad usually flat part of a leaf or petal. See line drawing of leaf and stem parts
Brackish: Slightly salty or having a high concentration of dissolved minerals.
Bract: A reduced or modified leaf associated with a flower or flower cluster.
Capsule: A dry, usually many-seeded fruit that splits open at maturity. See capsule line drawing
Compound: Divided into similar smaller parts united in one common whole such as leaves composed of two or more distinct leaflets. See the line drawing of a pinnately compound leaf
Corm:  A solid bulb-like stem usually found underground. See corm line drawing
Deciduous: Losing leaves seasonally - a maple tree is deciduous. 
Dioecious: Having male and female flowers on separate plants of the same species.
Eutrophic: Waterbodies characterized by high levels of nutrients (nitrogen and phosphorus)-often very productive systems with many aquatic plants and algae.
Exotic: Nonindigenous to a region or country
Flower: The reproductive part of the plant. Plants may have male only flowers, female only flowers, or both male and female flowers on the same plant. See the line drawing of flower parts
Freshwater: Non-salty water.
Fruit: The ripened ovary bearing the ripened seeds. See the line drawing for flower parts
Gland: A bump, depression, or appendage on a plantís surface that produces a sticky or greasy viscous fluid.
Habitat: The environment in which a plant lives.
Herb: A non-woody plant that dies back to the ground at the end of the growing season.
Holdfasts: Rootlike structures that anchor plantlike algae to the substrate.
Inflated: Hollow and swollen; appearing filled with air.
Invasive: Tending to spread and then dominate the new area.
Keel: The ridge of any structure formed by a fold, alluding to its resemblance to the keel of a boat.
Leaflet: A part or division of a compound leaf. See the line drawing of a compound leaf
Margin: Edge Ė as in the edge of a lake of the edge of a leaf. See line drawing
Midvein: The main central vein of a leaf. See the line drawing
Monoecious: Having male flowers and female flowers together on the same plant.
Nectary: A gland that secretes a sticky, often sweet-tasting fluid (nectar).
Non-native: Nonindigenous to a region or county; an introduced species.
Node: The place on the stem where a leaf, branch, or root is attached (or has been attached). See the line drawing
Nut: A hard, dry, usually one seeded fruit that does not open at maturity. Harder and thicker sided than an achene.
Nutlets: A small nut or a very thick walled achene.  Usually several produced by a single flower. See the line drawing
Oogonium: In algae, a female reproductive cell producing one or more eggs.
Opposite: Leaves arranged directly opposite of each other on each side of a node. See line drawing
Ovate: Shaped like a long section through a henís egg, broadest below the middle, narrowed at the tip. See the line drawing
Palmate: Divided into three or more lobes, leaflets or veins of a leaf that diverge from a common point like the fingers from the palm of a hand.  See line drawing
Pedicel: The stalk that supports one flower only when there are several on a peduncle. 
Peduncle: The stem of a solitary flower or the main stem of a flower cluster.
Perennial: A plant that lives for more than two years.
Perigynium: A sac enveloping a fruit in Carex spp. (sedges).
Petals: The inner ring of the flower. Often white or brightly colored to attract pollinators. (see sepal) See line drawing of flower parts
pH: The measure of the concentration of hydrogen ions. The acidity or alkalinity of the water. pH of 7 is neutral; below 7 is acid, above 7 is basic.
Pinnate: Feather-like, with a row of leaflets on either side of a central stalk.
Pistil: The female flower organ, consisting of the seed-bearing ovary, stigma and style. See line drawing of flower parts
Pith: Soft spongy tissue in the center of the stems and branches of certain species.
Pod: A dry fruit that splits open at maturity.
Pollen: Powdery grains which bear the sperm and are produced in the anther.
Rhizoid: A simple, root-like structure.  
Rhizome: A horizontal underground stem that is distinguished from the root by the presence of nodes or scale-like leaves. See line drawing
Rosette: A cluster of  leaves arranged in a circle usually at ground level (like a dandelion). See line drawing 
Saline: Salty or brackish
Scale: A small thin or flat outgrowth, often associated with underground parts, though leaves or bracts may be scale-like.
Sepals: The outermost ring of the flower; often green and leafy in structure. (see petal) See also flower parts drawing
Sessile: Attached directly to the base without a stalk.
Sheath: A tubular part surrounding another part, often papery.  In pondweeds the portion of the leaf that surrounds the stem. See line drawing of stem parts
Spike: A flower cluster with sessile flowers arranged along an unbranched stalk, blooming from the bottom upwards.
Spikelets: Small, much reduced spikes with few flowers.
Spores: The reproductive body of ferns and other non-seed plants Ė analogous to a seeds.
Stalk: A stem or similar structure that supports a flower, flower cluster, or a leaf.
Stamen: The male part of a flower usually consisting of the stalk-like filament and the pollen-bearing anther. See flower parts drawing
Stem: The part of the plant bearing leaves and flowers and composed of nodes and internodes (space between the nodes).  Sometimes also below ground (see rhizome, corm, stolon, tuber). See drawing
Stigma: The upper tip of the pistil of the flower, receives the pollen. See flower parts drawing
Stipules: A pair of wing or scale-like structures often found at the base of leaves.  Sometimes joined into a sheath.
Stolons: A stem that trails along the sediment or soil surface that forms roots at the nodes (strawberries spread by stolons). See line drawing
Style:  The stalk-like portion of the pistil between the stigma and the ovary. See flower parts drawing
Submersed: Growing underwater (submerged).
Subpalmate: Almost palmate.
Substrate: The sediment that plants root in.
Succulent: A fleshy plant that holds water in its stems or leaves.
Tepals: Petals and sepals that are almost indistinguishable from each other, as in rushes (Juncus sp).
Thallus: A main plant body not differentiated into stems and leaves as in duckweeds and liverworts.
Toothed: Saw-edged. See line drawing
Tubers: An enlarged, fleshy, reproductive and food-storage structure produced on an underground stem (a potato is a tuber). See line drawing
Turion: An overwintering structure that is scaley or often thick and fleshy that detaches, and then geminates or starts growth in the spring. See line drawing
Vascular: Refers to the circulatory system in plants or to plants with veins.
Vein: A circulatory structure often prominent in leaves. See line drawing
Whorls: A ring of 3 or more similar structures radiating from a common point (a whorl of leaves around a node). See line drawing
Winter buds: Structures that form on the plant in the fall, detach, and then germinate in the spring to form a new plant. Often look like compact bundles of small leaves. See turion line drawing

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