GLOSSARY 831 



Plutonic Rocks. — Eocks 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 adher- 

 ing 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. 



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 

 attacbment of muscles, ligaments, etc. 



Propolis. — A resinous material collected by the Hive-Bees 

 from the opening buds of various trees. 



Protean. — Exceedingly variable. 



Protozoa. — The lowest great division of the Animal King- 

 dom. These animals are composed of a gelatinous mate- 

 rial, and show scarcely any trace of distinct organs. Tlie 

 Infusoria, Foraminifera, and Sponges, with some other 

 forms, belong to this division. 



Pupa (pi. Pup^).— The second stage in the development of 

 an Insect, from which it emerges in the perfect (winged) 

 reproductive form. In most insects the pupal stage is 

 passed in perfect repose. The chrysalis is the pupal 

 state of butterflies. 



