Knight — 114 — Dictionary 



whose individuals are sexually reproductive, but which is com- 

 posed of intersterile segments (Camp & Gilly). 



Phenotype. — A group of individuals of similar appearance 

 but not necessarily of similar genetic constitution. 



Phenotypic. — Appertaining to the physical make-up of an 

 organism or group of organisms as distinct from their genetic 

 make-up. The phenotypic effect of any particular gene on an 

 organism is its outward, measurable, quantitative or qualita- 

 tive effect on that organism. 



Phenotypic Intersex. — An organism which though of one 

 sex in genetic origin, develops as a result of physiological 

 changes, organs or tissues characteristic of the other sex. 



Phenotypic Sex Determination. — A form of sex determina- 

 tion in which the influence of the environment in which the 

 new individual develops over-rides any genetical sex-mechan- 

 ism. 



Photoperiodism. — The governing of season of flowering by 

 the number of hours of daylight per day. See Long-day and 

 Short-day plants. Adj. Photoperiodic. 



Phyloephebic. — Pertaining to the phase of the life of a race 

 or individual when vigour is at its peak. 



Phylogenesis, Phylogeny. — The evolutionary history of a 

 species, genus or race. Adj. Phylogenetic. 



Phylogenetic Series. — An evolutionary chain of organisms, 

 most of the members of which are usually extinct, which in- 

 dicates the descent of present-day types from earlier forms. 



Phylogeny. — Phylogenesis, q.v. 



Phylogerontic. — Pertaining to the phase in the life of a 

 race (or individual) when senescence has begun, 



Phyloneanic. — Phyloephebic, q.v. 



Phylonepionic. — Pertaining to the phase in the life of a 

 race when the race is still young and has not reached its peak 

 of vigour. 



Phytogenesis. — The evolution and development of plants. 



Phytogenetics. — Plant genetics. 



Phytoplasm. — Plant protoplasm. 



Pin-eyed. — Having the stigma level with the throat of the 

 corolla and the anthers below, enclosed within the corolla-tube. 



Pistil. — The ovary style and stigma, collectively. 



Pistillate Flower. — A female flower lacking stamens. 



Placenta. — The membrane, or surface, bearing ovules in plants 

 and in animals a structure formed by the union of the allantois 

 and chorion with the uterine wall and providing for the respira- 

 tion and nutrition of the foetus. 



