446 APPENDIX 



OVULE. The body which after fertilization of the egg becomes a 

 seed. The ovule consists of protective envelopes (integument) 

 enclosing the nucellus (megasporangium) with the embryo sac 

 (megaspore) . 



OVULE CASE. The base of the pistil in which ovules arise. 

 "Ovary." 



OVUM. Egg. Female gamete. 



OXIDATION. The combination of any substance or its constituent 

 parts with oxygen. 



PALEONTOLOGY. The science of extinct animals and plants repre- 

 sented by fossil remains. 



PARASITE. An organism which secures its livelihood directly at the 

 expense of another living organism, on or in whose .body it lives. 



PARTHENOGENESIS. Development of an egg without fertilization. 



PATHOGENIC. Disease-producing, especially in regard to the rela- 

 tion of a parasite to its host. 



PEDUNCLE. Stalk of a flower; represents the floral branch. 



PENTADACTYL. Having five fingers or toes; typical Vertebrate 

 limb. 



PERIANTH. Collective term for calyx and corolla. 



PERICARDIUM. Peritoneum lining the pericardial cavity containing 

 the heart. 



PERISTALSIS. Rhythmical contractions of the wall of the alimen- 

 tary canal which forces the food along. 



PERITONEUM. Membrane lining coelom of Vertebrates. Consists 

 of an outer layer of connective tissue next to the muscles of body 

 wall and an inner layer of coelomic epithelium which forms the 

 innermost layer of body wall. 



PETAL. One of the leaves of the corolla of a flower. 



PETIOLE. A leaf stalk. 



PHARYNX. Region of alimentary canal between buccal cavity, or 

 mouth, and oesophagus. Throat. 



PHENOTYPE. The somatic, or expressed, characters of an organism 

 or group of organisms irrespective of those potential in their germ 

 cells. See Genotype. 



PHLOEM. The outer part of a vascular bundle. 'Inner bark.' 



