farr: cytokinesis of pollen-mother-cells 313 



unsatisfied soluble ions may diffuse outward in all directions from 

 the nuclei, possibly streaming along the paths in the colloidal 

 protoplasm marked by the fibers. The ions from different nuclei 

 would meet in an equatorial plane and might, if conditions admit, 

 form an undissolved compound. If, however, the cell was able 

 to admit w^ater and increase in volume in response to the increased 

 osmotic pressure, these salts might remain at a concentration 

 below the saturation point and hence not precipitate. May it 

 not be that such a condition exists in these mother-cells, which 

 are able to increase their volume considerably? On this in- 

 terpretation there would be in these mother-cells an invisible 

 cell-plate of soluble material, and the relation of division by 

 furrows to that of the ordinary type of higher plants becomes more 



comprehensible. 



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