ptenophyti´um (πτηνός, passing), an intermediate formation.
pterospore (πτερόν, wing), a plant with winged disseminules.
purpureus, purple.
pycnophyti´um (πυκνός, thick), a closed formation.
pyri´um (πῦρ, fire), a burn succession.
quadrat (quadratum, a square), a square meter of vegetation marked off for counting, mapping, etc.; major, a quadrat of 2–14 square meters.
reaction, the effect of the formation upon the habitat.
relict (relictus, left), a species belonging properly to an earlier type of succession than the one in which it is found.
repi´um (ῥέπω, sink), a succession due to subsidence.
rhoi´um (ῥόος, stream), a creek formation; rhoad, a creek plant.