Dictionary

Word	Meaning
Precocious	Ripening early or before its time.
Prickle	A hard pointed structure growing on a stem that arise from the epidermis, and not from vascular or woody tissue. Refer to spine.
Primary growth	Growth in an apical meristem.
Protandrous	A flower that sheds pollen before its stigma is receptive, to avoid self-pollination. Male functionally precedes female functionally.
Pseudaril	A structure that resembles an aril but is attached to the endocarp, not to the seed.
Puberulous	Covered with minute hairs or very fine down; finely pubescent.
Pubescent	Covered with short soft hair; downy. Refer to pilose.
Pulvinus	A swollen petiole at the leaf base that facilitates growth-independent movement. Asymmetric swelling and contraction of the pulvinus helps in periodic leaf movement. Pulvini are common in Fabaceae.
Pustulate	With slight blister-like elevations.
Putamen	A hard or stony endocarp.
Pyrene	The fruit-stone within a drupe or drupelet, produced by the ossification of the endocarp, or lining of the fruit.
Raceme	A simple inflorescence in which flowers are borne at equal distances along a single elongated axis, which continues to grow indefinitely. The flowers at the base of the central stem develop first. The flowers can be stalked or sessile (see spike). Compare with cyme and spike.
Racemose	The adjective form of raceme.
Rachilla	The central axes that bears the leaflets of a bipinnate leaf.
Rachis	The portion of the main axis of a compound leaf that bears the leaflets. The petiole ends and the rachis begins at the point of the first leaflets. Refer to rhachis.
Receptacle	A receptacle is the enlarged end of a pedicel, which is the stalk of a single flower. In a compound inflorescence, receptacles are the enlarged ends of peduncles or flower stalks. In a fig, the receptacle wraps around the hundreds of flowers it bears, thus forming the fig.
Recurved	Bent backwards, as in recurved thorns.
Reflexed	Curved backwards or downwards.
Reniform	Shaped like a kidney.
Repand	The margin is uneven or wavy, with shallow undulations. See sinuate margins.
resin	Resin is a hardened or viscous secretion produced by plants in response to injury, protecting the plant from pathogens and insects. Resins may also deter herbivores. Resin is not soluble in water.
Resin	Exudate from a cut or other damage to the plant, that hardens when exposed to air. Resin is not soluble in water, and it is not latex.
Reticulate	Net-veined. When the smallest veins of a leaf are interconnected to give the appearance of a mesh-like net.
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.