Keys Dictionary

Word	Meaning
Retuse	Having a rounded or obtuse apex, with a notch at the apex. The term usually refers to a leaf. Emarginate refers to a sharply pointed notch at the apex
Revolute	The margin of the leaf turns slightly downward, toward the underside of the leaf. Also referred to as 'rolled under'.
Rhachis	The rachis is the main axis of a compound structure. In compound leaves, then rhachis is that portion of the main leaf axis that bears the leaflets, commencing where the petiole ends at the first pair of leaflets. In inflorescences, the rhachis is the flower-bearing portion of an inflorescence above the supporting peduncle.
Rhizome	An underground stem, usually horizontal, with nodes, buds or scale-like leaves. A rhizome differs from a root in these respects. A rhizome produces new growth above ground each growing season.
Rhombic	If referring to a leaf, a leaf with four roughly equal sides, but unequal angles, like a modestly compressed square.
Rhomboid	If referring to a leaf, a leaf with four roughly equal sides, but unequal angles, like a modestly compressed square.
Riparian	Habitats along the edges of rivers, streams, lakes, and bodies of water.
riverine	Habitats on, or in, rivers, or in wetlands that have a flowing channel.
Rosette	A circle of leaves radiating outward from a short stem.
Rosulate	Refers to leaves radiating from a central point, usually at the apex of a stem.
Rotundate	Rotund, being between oblong and rounded.
Rugose	Wrinkled.
Rugulose	Having little wrinkles.
Saccate	Parts of a plant that are shaped like a pouch or sack.
Sagittate	Shaped like an arrow head, with two acute, pointed lobes at the base.
Samara	A single-seed dry, indehiscent fruit with between one and six firm, papery wings. Fruits in the Combretum or Terminalia genera are samaras. A samara is a modified achene, which is a one-seeded dry fruit with no wings, and with its seed having one point of attachment only.
Sap	Sap is a fluid that circulates through the vascular system of plants, moving water, minerals, and sugars between the roots, stems, and leaves. Xylem sap consists mainly of water and minerals absorbed by the roots and transported into the tree. Phloem sap consists mainly of sucrose and other organic compounds that the plant moves from leaves, where photosynthesis occurs, to other parts of the plant, as needed. Sap and latex are different.
Sapwood	Living outer wood of a trunk, as distinct from the dead heartwood.
Sarmentose	With long thin runners or rhizomes. Alternatively, with long whip-like branches.
Scabrate	Flecked. These are small sculpturing elements on the surface.
Scabrid	Sandpapery
Scalloped	A leaf margin with rounded teeth.
Scandent	Climbing or scrambling, but without the use of tendrils to grip. A liana is a woody climber supported by other vegetation
Schizocarp	A dry compound fruit that splits at maturity into two or more separate carpels, each remaining attached at the base of the schizocarp. A mericarp is an individual seed-bearing carpel of a schizocarp fruit, and is a perfect fruit in itself.
Sclereids	Thick-walled lignified plant cells that form small bundles of durable layers of tissue in most plants, often branched in shape. Sclereids form many hard structures such as seed coats and nut shells. Their primary function is for mechanical support and protection.
Sclerophyll	Vegetation adapted to long, dry and hot periods, with hard leaves, short internodes and leaves held parallel or oblique to direct sunlight. The word comes from the Greek sklēros for hard and phyllon for leaf.
Secondary growth	Growth in a lateral meristem.
Secretory cavities	Tiny cavities, roughly circular, within the leaf blade that secrete oils or resins. The leaves of many trees in the Rutaceae, or the Citrus family, have secretory cavities that emit a citrus-like scent when crushed.
Self-pollination	Transfer of pollen from the anther to the stigma of the same flower.
Sepal	Small leaf-like structures at the base of the flower, typically green. Collectively, the sepals comprise the calyx. A sepal is therefore a segment of the calyx.