- Raceme
- Diversely branching flowers.
- Rays (Ray Flowers)
- The strap-like, often sterile flowers, commonly called “petals” surrounding the flowerhead of a plant in the composite family.
- Receptacle
- The upper part of the stem from which the floral parts arise.
- Rectification
- The process of redistillation applied to essential oils to rid them of certain constituents.
- Refrigerant
- A cooling substance used to reduce fevers; a substance similar to an emollient but is particularly useful in treating burns and rashes.
- Resin
- An amorphous (shapeless), solid, or semi-solid substance produced by plants; prepared resins are oleoresins from which the essential oil has been removed.
- Resolvent
- Any medicine that reduces inflammation or swelling, including boils and tumours; a discutient; an agent which disperses swelling, or affects absorption of a new growth.
- Restringent
- An astringent or styptic.
- Reticulate
- Veins, fibers, or lines crossing like a network across the surface of a leaf.
- Rhinitis
- Inflammation of the nasal mucous membranes (rhino means nose).
- Rhizome
- A thick horizontal plant stem, partly along and partly under ground, that sends out shoots and leaves above and roots from the underside.
- Root
- The underground part of the plant that functions in absorption, aeration, food storage, and as a support system.
- Rosemarinic Acid
- The active constituent of rosemary. It fights nausea, intestinal gas, and indigestion, as well as being effective against headaches.
- Rosette
- Leaves which are closely arranged in a spiral.
- Rubefacient
- A substance that stimulates the flow of blood to the surface of the skin or irritates the skin.
Both will produce flushing. Ancient civilizations highly prized rubifacient herbs before the advent of modern cosmetics.
- Rutin
- A common flavonoid found in such plants as buckwheat and believed to strengthen blood vessels.
