Charles Darwin: The Origin of Species by means of Natural Selection

GLOSSARY 1. GLOSSARY OF THE PRINCIPAL SCIENTIFIC TERMS USED IN THE PRESENT VOLUME. (continued)

PELVIS.--The bony arch to which the hind limbs of vertebrate animals are articulated.

PETALS.--The leaves of the corolla, or second circle of organs in a flower. 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.