Physiological Drought 



The conditions that obtain when a plant wilts or suffers 

 from insufficient water although the habitat contains ample 

 water, cf. Aridity, Cold desert. 



Physiological Form 



See Biological race. 



Physiological Isolation 



The condition of organisms that have become isolated 

 because of their physiological requirements rather than be- 

 cause of other kinds of Barriers, cf. Isolation. 



Physiology 



The branch of biology that deals with the functions and 

 processes carried on by plants and animals. 



Physogastry 



The condition in some insects in which the body be- 

 comes swollen, soft, and white, as in some beetles. 



Phytocide 



A chemical substance that exerts a differential killing 

 effect within a crop, e. g., one variety but not the other 

 varieties killed by DDT in a barley crop. 



Phytocoenosis 



The totality of plants in a stand of vegetation, the entire 

 plant Community, cf. Biocoenosis. 



Phytocoenosfics 



The term preferred by Gams in place of Plant sociology. 



Phytogeography 



See Plant geography. 



Phytograph 



A polygonal diagram that expresses several kinds of com- 

 munity characteristics such as numerical abundance, fre- 

 quency index, size classes, and basal area on various axes for 

 a certain species of tree in a forest. 



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