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Term	Definition
Placenta laminar	A placentation type in which the ovules are attached to laminae that run vertically through much of the ovary as seen in medial longitudinal section.
Placenta oblique	A type of placentation in which the placenta is derived from a short, horizontally expanded lower septum that expands at a right angle to the upper septum and may be slightly upward and outward oriented at its end as seen in medial longitudinal section.
Placental unit	The smallest continuous part of the placenta to which ovules are attached.
Placentation	In broadest terms, the arrangement of ovules within the ovary. See axile, basal, free-central, and parietal placentation.
Placentation	In broadest terms, the arrangement of ovules within the ovary. The most basic type of placentation classifies species as having parietal, axile, or free-central placentation.
Placentation basal	A type of placentation in which the ovule is attached to the floor of the locule.
Placentation bilamellar	A type of placentation that runs the length of the locule with two rows of ovules attached to two lamellae.
Placentation free-central	A type of placentation in which the ovules are borne on a central column arising from the base of a unilocular ovary.
Plane	Referring to a structure that is flat, even, or level with the surface of the structure in which it occurs; i.e., without projectiing above the surface of an organ.
Plank buttress	A flattened, board-like buttress.
Plant holder for photography	Devices, such as those shown here, can be used to secure plants in fixed positions to make it easy to photograph them. Note that the alligator clamp at the end of a flexible wire can either be attached to a branch or the base can be coiled into a circle and the device placed on the ground or another object. For more information about plant collecting see Tropical Plant Collecting: From the Filed to the Internet. This book can be purchased at: http://tecceditora.com/ or Amazon.com.
Plant holders for photography	Devices used to hold specimens of Lecythidaceae in place for photography.
Plant succesion	The sequence of plant communities that follows after natural or human disturbance.
Pleionanthy (pleionanthic, pleionanthous)	Referring to plants that flower repeatedly; i.e., those that do not die after a single flowering. Same as polycarpous and iteroparous; opposite of hapaxanthic and monocarpic.
Plinervada	Se refiere a una disposición de los nervios en las hojas, en la que el nervio medio o principal está longitudinalmente acompanado por varios otros nervios secundarios similares que nacen en la base de la hoja o cerca de ésta; por ejemplo, en muchas Ericaceae o algunas Euforbiaceae
Pliveined (plinerved)	Referring to leaf blade venation in which the midvein is accompanied by several nearly equal secondary veins arising at or near the base; e.g., in many Ericaceae and some Euphorbiaceae.
Plumose	Feathery or bearing featherlike hairs or bristles.
Pneumatophore	An erect, aerial breathing root found in species of wet habitats such as mangrove swamps.
Pneumatophore	An erect, aerial breathing root found in species of wet habitats such as mangrove swamps and along periodically inundated river banks.
Pock marks	A non technical term used to describe small circular depressions on the external surface of bark.
Pod	The most common fruit of the Fabaceae; see legume.
Polar nuclei	Two nuclei that migrate to the center of the embryo sac and fuse with a male nucleus (sperm) to form the primary endosperm nucleus which divides and sometimes forms the endosperm.
Pollen	Male reproductive structures contained within the anther of the stamen and usually released at anthesis. Same as microgametophytes.
Pollen drop	A small drop of liquid similar to nectar that accumulates on the apex of the ovule of gymnosperms. The wind-dispersed pollen of gymnosperms lands on the pollination drop and when it dries the pollen is carried into the ovule where it eventually fertilizes the egg to produce an embryo. See A in the attached figure.
Pollen guide	Markings on a flower that apparently serve to guide pollinators to pollen which is the reward they receive from the flower. Some are visible to humans, but others are apparent to humans only through ultraviolet photography.
Pollen guide	Markings on a flower that apparently serve to guide pollinators to pollen which is the reward they receive for visiting the flower. Some pollen guides are visible to humans, but others are apparent to humans only through ultraviolet photography.
Pollen syntricolpate	A type of pollen in which the colpi unite at both poles of a pollen grain.
Pollen syntricolpate	A type of pollen in which the colpi unite at both poles of a pollen grain.
Pollinarium (plural = pollinaria)	The pollen-bearing structure of Orchidaceae composed of a viscidium, a stipe, and pollinia.
Pollination (pollinate}	The transfer of pollen from an anther in a flower to the stigma of the same or to a different flower of the same species by pollinators such as the wind, water, insects, and mammals. Pollinate is the act of pollination.
Pollinator	An agent, such as the wind, water, some insects, and some mammals, that moves pollen from an anther in a flower to the stigma of the same flower or to the stigma of a different flower of the same species.
Pollinator guide	Markings on a flower that apparently serve to guide pollinators to pollinator rewards, generally pollen or nectar. Some are visible to humans, but others are apparent to humans only through ultraviolet photography. Same as pollen guide or nectar guide.
Pollinator reward	A general term that refers to a reward that an animal pollinator gets when it visits a flower. The reward is usually pollen or nectar.
Pollinium (plural = pollinia)	An aggregate pollen mass characteristic of Orchidaceae and those of Apocynaceae subfamily Asclepiadoideae.
Polyandrous	Referring to an androecium with numerous stamens. Same as polystemonous.
Polycarpy (polycarpic or (polycarpous)	Referring to plants that flower repeatedly; i.e., those that do not die after a single flowering. Same as iteroparous and pleionanthic; opposite of monocarpic, hapaxanthic and semelparic.
Polygamodioecy (polygamodioecious)	Referring to the sexual condition of a species that bears (male) staminate and bisexual (perfect) flowers on some plants and female (pistillate) and bisexual flowers on other plants.
Polygamomonoecy (polygamomonoecious)	Referring to the sexual condition of a species that bears staminate, pistillate, and bisexual flowers on the same plant. Same as trimonoecious.
Polygamous	Referring to the sexual condition of a species that bears bisexual and unisexual flowers on the same plant, e.g., an andromonoecious plant (with male [staminate] and female [pistillate] species is one example of a polygamous species.
Polypetalous corolla	Having petals free from one another. Same as choripetalous; opposite of sympetalous.
Polyphyletic	The inclusion of more than one evolutionary line in a taxonomic group.
Polyploidy	Referring to a process in which more than two sets of chromosome numbers are present. This is often the result of hybridization.
Polystemonous	Having many stamens. Same as polyandrous.
Polysymmetric flower	A flower, capable of being divided, by more than one line passing through the middle of the flower, into two equal parts that are mirror images of one another; e.g., in Gustavia (Lecythidaceae), species of Myrtaceae, and species of Rubiaceae. Same as acinomorphic, radially symmetrical, and regular flowers and opposite of zygomorphic, monosymmetric, bilateral, and irregular flowers. This term can refer to other plant parts as well.
Pome	An indehiscent fleshy fruit consisting of seeds surrounded by the pericarp which is in turn are surrounded by fleshy tissue derived from the hypanthium. This fruit type is found in species of Rosaceae subfam. Maloideae. Because part of the fruit is derived from the hypanthium, i.e. both the ovary and the hypanthium are part of the fruit, a pome is also considered to be a type of accessory fruit.
Poricidal anther dehiscence	Referring to anthers that shed their pollen via terminal apertures; e.g., Gustavia spp. (Lecythidaceae) and Solanum spp. (Solanaceae).
Poricidal capsule	A capsule that opens via apical pores, e.g., species of the genus Papaver.
Poricidal dehiscence	Opening via pores; usually applied to anthers that shed their pollen via terminal apertures, e.g., Gustavia spp. (Lecythidaceae) and Solanum spp. (Solanaceae) or to capsular fruits (e.g., species of Papaver).
Posterior end of flower	In neotropical Lecythidaceae, the side of the flower from which the ligule arises.
Posterior hood extension	An extension from the androecial hood split that gives rise to staminodes and/or vestigial stamens that are swept inward.
Predation	Referring to an interaction between two organisms one that lives on and at the expense of another, e.g., an insect larva that eats the embryo of a hickory nut or a species of Loranthaceae taking nutrients from a host plant.
Prickle	A sharp, pointed outgrowth of the epidermis of stems, leaves and other plant parts; e.g., on the trunk and branches of Ceiba pentandra (Bombacaceae) and Jacaratia spinosa (Caricaceae), on the stems of Smilax spp. (Smilacaceae), and on the stems and leaves of many species of Solanum.
Primary hemiepiphyte	Referring to a plant (e.g., Clusia spp. and species of Araceae) that begins its epiphytic life without a connection to the ground but later develops aerial roots that reach the ground.
Primary leaflet	The first division of a compound leaf.
Primary rachis	The main rachis of a compound leaf or a compound inflorescence.
Primary vein	The thickest vein of a leaf (Hickey, 1973)
Primary venation	The largest (in diameter) vein (e.g., in camptodromous venaton) or veins (e.g., in actindodromous venaton) in a leaf blade. Same as midrib.
Prominent (diminuitive = prominulous)	Raised above the surface; e.g., the veins of a leaf or a seed.
Prop roots	Aerial, densely packed, adventitious roots that are circular in transverse section. Prop roots do not allow light to be seen through them whereas stilt roots do.
Prophyll	In monocots, the first leaf produced on a branch and located between the branch and the main axis; often two-keeled.
Prostoma (plural = prostomata)	An indented and/or membranous area through which plant-associated ants bore into the hollow chambers of the trunks and stems; e.g., in many species of Cecropia (Cecropiaceae).
Prostrate	Creeping flat along the ground, usually referring to stems growing along the ground that produce roots at their nodes. Same as repent.
Protandry (protandrous)	Referring to a flower in which the pollen is shed before the stigma is receptive. Sometimes called proterandry (proterandrous).
Prothallus (plural = prothalli)	The structure representing that part of a fern's life cycle between the germination of the haploid spore and the formation of the zygote. Fern prothalli are small, green, often heart-shaped, and bear the archegonia and antheridia where the egg and sperm are produced, respectively.This is the gametophyte generation of ferns and is completely independent of the sporophyte generation. Only those who know what they are looking for can find prothalli because they are small and hidden among the debris on the ground.
Protogyny (protogynous)	Referring to a flower in which the stigma is receptive before the pollen is shed. Sometimes called proterogyny (proterogynous).
Protologue	A scientic publication in which a new species is described or a scientific publication in which more than one new species are described, in the latter case each of the descriptions is the protologue of the new species.
Proximal	Near to the place of attachment. Opposite of distal. Same as basal.
Proximal	The part of an organ closest its the point of attachment.
Pseudanthium (plural = pseudanthia)	A false flower; e.g., the inflorescence of species of Asteraceae and Dalechampia (Euphorbiaceae).
Pseudaril	In Burseraceae, soft aril-like tissue that covers part or all of the pyrene and attracts dispersal agents.
Pseudobulb	In Orchidaceae, a specially modified stem that is variously swollen and stores food and water. Pseudobulbs are common in epiphytic but are lacking in terrestrial species.
Pseudocarp	Several small "fruits" surrounded by accompanying parts, such as that of Siparuna (Siparunaceae), in which the separate carpels are surrounded by a fleshy hypanthium, or the syconia of figs in which the the achenes are surrounded by hollow stem ends.
Pseudostem	The apparent stem of Musa (Musaceae), Phenakospermum (Strelitziaceae), and some other monocots which is actually a cylinder formed by overlapping leaf bases.
Pseudostipule	A leaf (e.g., in some species of Aristolochiaceae) or leaflet (e.g., in some species of Trichilia, Meliaceae) that resembles a stipule; in some Bignoniaceae, a bud scale derived from the axillary buds that resembles a stipule.
Pseudosyncarpous	In the Annonaceae, referring to fruits in which the carpels seem to be connate, but in reality are free or almost free (e.g., species of Duguetia in the Annonaceae).

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