Regular, symmetrical in form; uniform in shape or structure.
Retrorse, directed backward or downward.
Revolute, rolled backward from the margins or apex.
Rhomboidal, quadrangular, with the lateral angles obtuse.
Rudiment, an imperfectly developed and functionally useless organ.
Rugose, wrinkled; ridged.
Saccate, sac-shaped; baggy.
Sagittate, shaped like an arrowhead; triangular, with basal lobes prolonged downward.
Salver-form, narrowly tubular, with limb abruptly or flatly expanded.
Scabrous, rough to the touch.