318 GLOSSARY, 



Pedunculated. — Supported upon a stem or stalk. The peduncu- 

 lated oak has its acorns borne upon a footstalk. 



Peloria or Peloeism. — The appearance of regularity of structure 

 in the flowers of plants which normallj bear irregular flowers. 



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 super- 

 ficial parts of animals. The cells secreting it are called pig- 

 ment-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 Mam- 

 malia. 



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-germiijated plants. 



Plutonic Rooks. — Rocks supposed to have been produced by igne- 

 ous 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-tubeg) which issue 

 from the pollen-grains adhering to the stigma, and penetrate 

 through the tissues until they reach the ovary. 



PoLTANDROus (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 Sea-mats. 



