cable to conscious cooperation of human beings, cf. Com- 

 mensalism, Symbiosis. 



Protogynous 



Refers to a flower that produces pollen when its stigma 

 is no longer receptive to pollen, cf. Protandrous. 



Protonema 



The branched filament of the Gametophyte (q. v.) gen- 

 eration that develops from a spore in mosses, and produces 

 leafy branches. 



Protoplasm 



The living material in cells of animals and plants, usually 

 differentiated into nucleus and cytoplasm. 



Protoplast 



The organized protoplasmic contents of a cell, used par- 

 ticularly in plants to distinguish the cell wall from the parts 

 within. 



Protozoan 



An animal, unicellular or non-cellular in the phylum 

 Protozoa. 



Provenance 



The place of origin of seeds or other Propagules. 



Psammolittoral 



The sandy shore of a lake. 



Psammon 



The assemblage of organisms that live in the water in 

 the interstices between sand grains in the Psammolittoral 

 (q. v.). 



Psammophyte 



A plant that grows in sandy soil. cf. Hydrophyte. 



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