260 THE OPEN BOOK OF NATURE 
Photo-micrography : The process of taking photographs of 
microscopic objects. 
Pinnate : Leaflets arranged on opposite sides of a common leaf- 
stalk. 
Pleistocene : The latest of the five periods of the Cainozoic Era. 
Plesiosaurus : An extinct kind of sea-reptile. 
Pliocene : The fourth of the five periods of the Cainozoic Era. 
Plumule : The ascending leafy part of a young plant, or growing 
embryo. 
Plutonic : Igneous rocks which have cooled at great depths below 
the surface of the earth. 
Pollen : The fertilizing dust contained in the anthers of stamens. 
Pollinium : The pollen masses of orchids. 
Polyps : Animals like the hydra or the corals. 
Porifera : The sponges. 
Proboscis ; The trunk which is used for conveying food to the 
mouth. 
Process : In botany or biology, a projection or growth proceeding 
from the stem or body. 
Protozoa : A group of one-celled animals having no body cavity 
or nervous system. 
Pseudopodia : The “false feet’ or processes which protozoons 
use in their movements. 
Pteranodon : An extinct flying reptile. 
Pterichthys : An extinct fish. 
Pterodactyles : Extinct flying reptiles. 
-Pterygotus : An extinct Crustacean. 
Pupa : The chrysalis form of insects. 
Pyrites : A sulphide of iron which forms bright, brassy crystals. 
Quartz: A crystalline oxide of silicon commonly occurring in 
veins of rocks. 
Quartzite : A sandstone or grit affected by contact with igneous 
masses, and metamorphosed and hardened by the heat. 
Quaternary : Another name for the Pleistocene Period. 
Radical : Springing from a point just above the root. 
Radiolaria : Marine protozoons which build flinty skeletons, 
through apertures of which they protrude parts of their 
bodies in a ray-like manner. | 
Receptacle : The swelled top of a flower-stalk bearing the flowers 
of a composite. The support of the parts of a flower. 
Reniform : Kidney-shaped. 
Reptiles: Animals covered with scales or plates and which 
breathe entirely by lungs. 
Reticulated : Forming a network. 
Rhizome : A prostrate stem sending roots into the earth. 
Rugose : Wrinkled. 
