Pathotype — 113— Phenon 



different tissues, one being external to, and surrounding the 

 other, 



Perigynous. — Calyx, corolla and stamens borne on a rim 

 of the receptacle so that they are on the same level as the ovary. 



Periplast. — Cytoplasm, q.v. 



Perisphere. — The peripheral portion of the attraction sphere. 



Permanent Hybrid. — A hybrid which is pure breeding by 

 reason of the suppression of certain phenotypes by lethal fac- 

 tors. 



Perultimate Chromomere. — Telomere, q.v. 



Petaliform. — Petal-like. 



Petalody. — The state of having one or more of the floral 

 whorls petaliform, in addition to, or instead of, the corolla. 



Petaloid. — Petal-like. 



Pfluger's Egg Cords. — Columns of cells which, in the em- 

 bryo, grow from the germinal epithelium down into the stroma 

 and which give rise, in the male, to the testes, and in the 

 female to the ovaries. 



pH. — A measure of hydrogen-ion concentration. /jH less 

 than 7 shows acidity, pYi 7 is neutral and pYi more than 7 

 alkaline. 



Phaenogenetics. — Phenogenetics, q.v. 



Phenocontour. — A line showing the geographic distribution 

 of races with equal phenotypic manifestation; isomar. 



Phenocontour Map. — A map showing the geographic distri- 

 bution of the polymorphic forms of a species, areas with a 

 similiar percentage of one form (as compared with the popu- 

 lation) being marked off by phenocontours or isomars (iso- 

 phenes). 



Phenocopies. — Environmentally produced imitations of gene 

 mutants. 



Phenogenetics. — The study of ontogeny to find the stage of 

 development at which the difference between types first be- 

 comes manifest (de Beer). Developmental genetics; that 

 part of genetics which deals with the genetic control of the 

 development of the outward, visible or concrete characters of 

 an organism. Adj. Phenogenetic. 



Phenogens. — Units of a phenon which are intersterile but 

 which can not be distinguished except by genetic analysis. 



Phenological Isolation. — Biologic isolation of one species 

 or group from the other members of the genus by reason of 

 differences in time of flowering. 



Phenon. — A species which is phenotypically homogeneous and 



