potometer (ποτόν, drink), an instrument for measuring absorption.
prevernal, pertaining to early spring.
prior, earlier, used of alpine aspects.
prochosi´um (πρόχωσις, a deposition of mud), a succession in an alluvial soil.
prodophyti´um (πρόοδος, pioneer), an initial formation.
protodoche (πρῶτος, first), a primary succession.
proximity (proximitas, nearness), nearness to the area invaded.
psamathi´um (ψάμαθος, sand of the seashore), a strand formation; psamathad, a strand plant; psammogenous (ψάμμος, sand), producing a sandy soil.
psili´um (ψιλά, land without trees), a prairie formation; psilad, a prairie plant.
psychrometer (ψυχρός, chill), an instrument that measures humidity by means of a fall in temperature; psychrograph, a psychrometer that records automatically.