They are usually of delicate texture and brightly coloured.
PHYLLODINEOUS .-- Having flattened, leaf-like twigs or leafstalks instead of true leaves.
PIGMENT .-- The colouring material produced generally in the superficial parts of animals.

The cells secreting it are called PIGMENT-CELLS.
PINNATE .-- Bearing leaflets on each side of a central stalk.
PISTILS .-- The female organs of a flower, which occupy a position in the centre of the other floral organs.

The pistil is generally divisible into the ovary or germen, the style and the stigma.
PLACENTALIA, PLACENTATA .-- or PLACENTAL MAMMALS, See MAMMALIA.
PLANTIGRADES .-- Quadrupeds which walk upon the whole sole of the foot, like the bears.
PLASTIC .-- Readily capable of change.
PLEISTOCENE PERIOD .-- The latest portion of the Tertiary epoch.
PLUMULE (in plants) .-- The minute bud between the seed-leaves of newly-germinated plants.
PLUTONIC ROCKS .-- Rocks supposed to have been produced by igneous action in the depths of the earth.
POLLEN .-- The male element in flowering plants; usually a fine dust produced by the anthers, which, by contact with the stigma effects the fecundation of the seeds.

This impregnation is brought about by means of tubes (POLLEN-TUBES) which issue from the pollen-grains adhering to the stigma, and penetrate through the tissues until they reach the ovary.
POLYANDROUS (flowers) .-- Flowers having many stamens.
POLYGAMOUS PLANTS .-- Plants in which some flowers are unisexual and others hermaphrodite.

The unisexual (male and female) flowers, may be on the same or on different plants.
POLYMORPHIC .-- Presenting many forms.
POLYZOARY .-- The common structure formed by the cells of the Polyzoa, such as the well-known seamats.
PREHENSILE .-- Capable of grasping.
PREPOTENT .-- Having a superiority of power.
PRIMARIES .-- The feathers forming the tip of the wing of a bird, and inserted upon that part which represents the hand of man.
PROCESSES .-- Projecting portions of bones, usually for the attachment of muscles, ligaments, etc.
PROPOLIS .-- A resinous material collected by the hivebees from the opening buds of various trees.
PROTEAN .-- Exceedingly variable.
PROTOZOA .-- The lowest great division of the animal kingdom.