Simple. Of one piece; not compound.
Sinuate. With the outline of the margin strongly wavy.
Sinus. The cleft or recess between two lobes.
Smooth. Without roughness or pubescence.
Sorus (pl. Sori). A heap or cluster, applied to the fruit-dots of Ferns.
Spadix. A spike with a fleshy axis.
Spathe. A large bract or pair of bracts enclosing an inflorescence.
Spatulate. Gradually narrowed downward from a rounded summit.
Spicate. Arranged in or resembling a spike.
Spiciform. Spike-like.