_Prostrate._ Lying flat upon the ground.

_Proterogynous._ Having the stigma ripe for the pollen before the maturity of the anthers of the same flower.

_Prothallus._ A cellular usually flat and thallus-like growth, resulting from the germination of a spore, upon which are developed s.e.xual organs or new plants.

_Pseudaxillary._ Terminal but becoming apparently axillary by the growth of a lateral branch.

_Pseudo-costate._ False-ribbed, as where a marginal vein or rib is formed by the confluence of the true veins.

_Pteridophytes._ Fern-plants; Ferns and their allies.

_p.u.b.erulent._ Minutely p.u.b.escent.

_p.u.b.escent._ Covered with hairs, especially if short, soft and downy.

_Punctate._ Dotted with depressions or with translucent internal glands or colored dots.

_Puncticulate._ Minutely punctate.

_Pungent._ Terminating in a rigid sharp point; acrid.

_Putamen._ The sh.e.l.l of a nut; the bony part of a stone-fruit.

_Quadrate._ Nearly square in form.

_Raceme._ A simple inflorescence of pedicelled flowers upon a common more or less elongated axis.

_Racemose._ In racemes; or resembling a raceme.

_Radiate._ Spreading from or arranged around a common centre; bearing ray-flowers.

_Radical._ Belonging to or proceeding from the root or base of the stem near the ground.

_Radicle._ The portion of the embryo below the cotyledons, more properly called the caudicle.

_Radiculose._ Bearing rootlets.

_Rameal._ Belonging to a branch.

_Ramification._ Branching.

_Ray._ The branch of an umbel; the marginal flowers of an inflorescence when distinct from the disk.

_Receptacle._ The more or less expanded or produced portion of an axis which bears the organs of a flower (the _torus_) or the collected flowers of a head; any similar structure in Cryptogams.

_Recurved._ Curved downward or backward.

_Reflexed._ Abruptly bent or turned downward.

_Regular._ Uniform in shape or structure.

_Reniform._ Kidney-shaped.

_Repand._ With a slightly uneven and somewhat sinuate margin.

_Resiniferous._ Producing resin.

_Reticulate._ In the form of network; net-veined.

_Retrorse._ Directed back or downward.

_Retuse._ With a shallow notch at a rounded apex.

_Revolute._ Rolled backward from the margins or apex.

_Rhachis._ The axis of a spike or of a compound leaf.

_Rhaphe._ The ridge or adnate funicle which in an anatropous ovule connects the two ends.

_Rhizome._ Any prostrate or subterranean stem, usually rooting at the nodes and becoming erect at the apex. Very variable in character, and including morphologically the tuber, corm, bulb, etc.

_Rhombic, Rhomboidal_, Somewhat lozenge-shaped; obliquely four-sided.

_Rib._ A primary or prominent vein of a leaf.

_Ringent._ Gaping, as the mouth of an open bil.a.b.i.ate corolla.

_Root._ The underground part of a plant which supplies it with nourishment.

_Rootstock._ Same as Rhizome.

_Rostrate._ Having a beak or spur.

_Rosulate._ In the form of a rosette.

_Rotate_ (corolla). Wheel-shaped; flat and circular in outline.

_Rotund._ Rounded in outline.

_Rudiment._ A very partially developed organ; a vestige.

_Rudimentary._ But slightly developed.

_Rufous._ Reddish brown.

_Rugose._ Wrinkled.