THE EMBRYO-SAC AND POLLEN GRAIN AS 

 COLLOIDAL SYSTEMS 



Francis E. Lloyd 



McGill University 



One of the most Insistent problems of the present time In the 

 field of biology Is the relation of growth to the behavior of colloids, 

 especially those known as emulsion-colloids.^ These bodies show 

 the phenomena of swelling at low concentrations of acids and 

 alkalis, and of shrinkage in salts. Certain of them (albumin, 

 etc.) coagulate irreversibly at high temperatures, with concen- 

 trations of acids in wide amplitudes, possibly (as indicated by 

 my own experiments) at certain concentrations of alkalis, by 

 mechanical disturbance (shaking, pressure) ; and to this group of 

 bodies protoplasm belongs. It seems now clear that protoplasm 

 is a hydrophile emulsion colloid, the hydratatlon capacities of 

 which are functions of the solutes in the watery medium which 

 bathe it. Any change in the concentrations of the solutions must 

 cause corresponding changes In the amount of water within the 

 protoplasm, and this must change the spacial relations of the 

 water-poor dispersolds and water-rich disperse medium, evidenced 

 In swelling or shrinkage. Changes in surface tensions, electrical 

 charge, etc., may be mentioned as Indicating the vast possibilities 

 which can result. One possible and important result is the 

 change in permeability which can be readily conceived as being 

 a function of the changes In spacial relations above mentioned. 

 When the antagonistic effects of mixed solutes, the coagulating 

 effects of various reagents, and the possible dissolution of sub- 

 stances (such as lipoid), either proper to or associated with proto- 

 plasm by appropriate solvents, are added as further possibilities 

 of affecting the Internal relations, It becomes at once evident that 

 the problems in this field are both complex and difficult. 



For the present purpose, one such difiiculty which confronts the 

 experimental cytologist is the presence of water vacuoles In the 

 majority of growing plant cells. It has indeed been assumed, by 



^ Such as jelly of any kind, protein bodies in unpeptlzed condition, such as protoplasm. 

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