438 Glossary. 



Papilionace^e. — An order of Plants (see Leguminos^e). — The flowers of 

 these plants are called papilionaceous, or butterfly-like, from the 

 fancied resemblance of the expanded superior petals to the wings of a 

 butterfly. 



Parasite. — An animal or plant living upon or in, and at the expense of, 

 another organism. 



Parthenogenesis. — The production of living organisms from unimpreg- 

 nated eggs or seeds. 



Pedunculated. — Supported upon a stem or stalk. The pedunculated oak 

 has its acorns borne upon a footstalk. 



Peloria or Pelorism. — The appearance of regularity of structure in the 

 flowers of plants which normally 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 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 pro- 

 duced 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 Sea-mats. 



Prehensile. — Capable of grasping. 



Prepotent. — Having a superiority of power. 



