Forest Home

Welcome to Ariadne's Forest Glossary

Glossary: P is for ... polygamous pioneer population.
by Ariadne Unst

Glossary of P...

palmate (adj.)
Radiating from a single point like the spreading fingers of an outstretched hand.

Pangea (n.)
The single continent formed 400 MYA from collision of the ancient continents of Gondwanaland, Laurentia, and others.

panicle (n.)
A loose compound flower (inflorescence) produced by branching. The branches are in a raceme and the flowers have a pedicel.

parasite (n.)
An organisms that lives on another (its host), from which it obtains food and shelter. As the parasite depends upon the host, it usually does not kill the host but harms it by causing the host to use some of its resources to feed the parasite.

parenchyma (n.)
Soft cell tissue of plants. Found in stem pith and in pulp of some fruits.

parsimony, principle of (n.)
If two answers exist to a problem or a question, and if, for one answer to be true, well-established laws of logic and science must be modified, ignored, or suspended, while for the other answer to be true no such sleight-of-hand is needed, then the simpler of the two answers (the second) is much more likely to be correct. (parsimonious, adj.)

pathogen (n.)
An organism or substance that causes disease. Includes parasitic microorganisms (bacteria, viruses), fungi, and larger parasitic plants and animals.

peat (n.)
Undecomposed or only slightly decomposed organic matter accumulated under conditions of excess moisture. Semi-carbonized remains of plants (such as moss, sedge, trees), some animal residues, and often some mineral soil. Plant residues show little, if any, morphological change.

pedicel (n.)
The stalk supporting a single flower that is part of an inflorescence upon a peduncle

pedocals (n.)
Soils rich in calcium. Formed where water is scarce, so there is less leaching of salts from the soils.

peduncle (n.)
The stalk of a flower cluster or of a solitary flower.

perennial (n.)
A plant that lives more than two years.

perfect flower (n.)
A flower having both stamens and carpels; may or may not have a perianth.

perianth (n.)
A collective term for the floral envelopes, usually the combined calyx and corolla of a flower.

pericarp (n.)
The wall of a ripened ovary (fruit). It is homogeneous in some genera. In others it is composed of three distinct layers, exocarp, mesocarp, and endocarp.

permafrost (n.)
Permanently frozen ground; generally refers to a layer at some depth below the soil surface. Persists over at least two consecutive winters and the intervening summer. A layer above it, which thaws in summer, is the active layer.

pest (n.)
Any species that is considered obnoxious (usually with regard to its interference with human commercial and/or convenience interests).

petal (n.)
Part of the corolla; one of a circle of modified leaves surrounding the reproductive organs and usually brightly colored.

petiole (n.)
The stem of a leaf; the leafstalk.

phenotype (n.)
The plant as observed. The product of the interaction of the genes of an organism (the genotype) with the environment.

phloem (n.)
The layer of cells that forms a pipeline to carry sugars and other food materials from the leaves (where they are produced) to the branches, roots, and the rest of the tree. The cells produced on the outside of the cambium become part of the phloem. Some of the phloem cells age and die each year, and they become part of the outer bark.

photosynthesis (n.)
Chemical process in the cells of green plants, which form carbohydrates and atmospheric oxygen from carbon dioxide and water, through sunlight acting on chlorophyll. The chemical elements that are reorganized are carbon, oxygen, and hydrogen.

phylogeny (n.)
The history of the evolution of a species or group. The evolutionary development and history of a species or higher taxonomic grouping of organisms. Sometimes called a family tree.

phylum (n.)
A division of plants and animals. It ranks below a kingdom and above a class. Its members are believed to have a common evolutionary ancestor. Also called subkingdom.

pinnae (n.)
Divisions (leaflets) of a compound leaf.

pinnate (adj.)
Like a feather; having the arrangement and shape of a feather, with segments arranged feather-like on either side of a common axis.

pioneer (n.)
A species adapted to be a good invader of a newly exposed soil surface, where it persists until supplanted by successor species. Usually a pioneer plant has small, windblown seeds or other properties that facilitate their distribution.

pistil (n.)
Ovule-bearing organ of an angiosperm composed of ovary, style, and stigma.

Pleistocene (n.)
[Greek pleistos = most and kainos = new, recent.] The time period from 1 MYA (million years ago) to 10,000 years ago. During this time, glaciation advanced and retreated several times, and man evolved physically and evolved psychologically.

polyandrous (adj.)
Plants bearing many stamens.

polyanthous (adj.)
Plants bearing many flowers.

polycephalous (adj.)
Plants bearing many flower heads

polygamous (adj.)
Plants bearing both perfect and imperfect (unisexual and bisexual) flowers.

polymorph (n.)
One of several forms of an organism.

population (n.)
A group of interbreeding individuals of the same species; they are separated but not isolated from other interbreeding groups of the same species.

protein (n.)
Any of the highly complex nitrogenous organic compounds. They are synthesized by plants and are a chief component of living matter.

proximal (adj.)
Relatively near the central axis or the point of attachment.
Compare distal.

pteriodophyte
A subdivision of vascular plants that consists of ferns and their allies. Contrast with spermatophyte.

pterocarpous (adj.)
Having winged fruits.

pterospermous (adj.)
Having winged seeds.

pubescence (n.)
A growth of hair or fine down on plants.