PHYTOLOGY, the study of plants; same as botany. PHYTOZOA, moving filaments in the antheridia of cryptogams. PILEATE, having a cup or lid like the cup of a mushroom. PILEORHIZA, a covering of the root, as in _Lemna_. PILEUS, the cap-like portion of the mushroom, bearing the hymenium on its under side. PILOSE, provided with hairs; applied to pappus composed of simple hairs. PINNA, the leaflet of a pinnate leaf. PINNATE, a compound leaf having leaflets arranged on each side of a central rib. PINNATIFID, a simple leaf cut into lateral segments to about the middle. PINNATIPARTITE, a simple leaf cut into lateral segments, the divisions extending nearly to the central rib. PINNULE, the small pinnæ of a bipinnate or tripinnate leaf. PISTIL, the female organ of the flower, composed of one or more carpels; each carpel being composed of ovary, style, and stigma. PISTILLATE and PISTILLIFEROUS, applied to a female flower or a female plant. PISTILLIDIUM, the female organ in cryptogams. PITCHERS, vessels of this form at the end of the leaves of _Nepenthes_, etc. PITH, same as Medulla. PLACENTA, the cellular part of the carpel, bearing the ovule. PLACENTATION, the formation and arrangement of the placentas. PLEURENCHYMA, woody tissue. PLEUROCARPI, mosses with the fructification proceeding laterally from the axils of the leaves. PLICATE, folded like a fan. PLUMOSE, feathery; applied to hairs having two longitudinal rows of minute cellular processes. PLUMULE, the first bud of the embryo, usually inclosed by the cotyledons. PLURILOCULAR, having many loculaments. PODETIUM, a stalk bearing the fructification in some lichens. PODOSPERM, the cord attaching the seed to the placenta. POLLARD-TREES, cut down so as to leave only the lower part of the trunk, which gives off numerous buds and branches. POLLEN, the powdery matter contained in the anther. POLLEN-TUBE, the tube emitted by the pollen grain after it is applied to the stigma. POLLINIA, masses of pollen found in orchids and asclepiads. POLYADELPHOUS, stamens united by their filaments so as to form more than two bundles. POLYANDROUS, stamens above twenty. POLYCARPIC, plants which flower and fruit many times in the course of their life. POLYCOTYLEDONOUS, an embryo having many cotyledons, as in firs. POLYGAMOUS, plants bearing hermaphrodite as well as male and female flowers. POLYMORPHOUS, assuming many shapes. POLYPETALOUS, a corolla composed of separate petals. POLYPHYLLOUS, a calyx or involucre composed of separate leaflets. POLYSEPALOUS, a calyx composed of separate sepals. POME, a fruit like the apple and pear. POROUS VESSELS, same as pitted or dotted vessels. POSTERIOR, applied to the part of the flower placed next the axis; same as Superior. POUCH, the short pod or silicle of some _Cruciferæ_.