68 CARNEGIE INSTITUTION OF WASHINGTON. 



Structure of the protoplast.^ — The cytoplasm appears as a colorless, 

 glistening mass. Only a ver}'- slight lack of homogeneity allows the 

 inference of ''granulation." No water vacuoles and no solids are 

 visible. On applying a concentrated salt solution (3 /N KNO3) swelling 

 slowly follows initial shrinkage, during which an emulsion-Uke structure 

 is optically accentuated. 



A lipoid is present in amicronic dispersion and is apparently dis- 

 tributed throughout the whole of the cytoplasm. The alterations 

 of surface tensions on swelling, on consequent pressure on the envelope 

 (this being a possible factor), and on coagulation, causes changes in 

 the degree of dispersion- and the lipoid becomes segregated into visible 

 droplets, which are usually smaller toward the periphery (in 0.7/jN. 

 NH4OH) and frequently absent from a peripheral zone (in KNO3,0.6/N). 

 This behavior is strongly suggestive of that of the fluid disperse phase 

 in relation to the fluid disperse medium of the protoplasmic emulsion 

 colloid proper, and further that changes in permeability can be explained 

 as changes in the size of the fluid suspensoids and in their spatial 

 relations in the disperse medium.^ Such changes may be reversible, as 

 when a previous volume, follow^ing shrinkage caused by a salt, is 

 restored, or irreversible, as when coagulation has occurred. Altera- 

 tions in permeability could thus be caused by mechanical pressure, or 

 application of salts, or other dehydratating agent (such as glycerine), 

 hydratating agents (acids, alkalis), heat, or any other conditions which 

 would temporarily or permanently alter surface-tension conditions, or 

 the amount of water held within the critical colloid complex. The 

 ''normal" condition of the protoplast is one adjusted to the substances 

 present in itself and in the solutions within the vacuoles, if these are 

 present, so that the application of (e. g.) distilled water or water of lower 

 concentration must produce changes in hydratation, and hence of 

 permeability. 



The mutual effects of two reagents, one a salt and the other acid or 

 alkali, are of interest in this connection. A 10 per cent (or 1 per cent) 

 solution of ammonia will cause the contents of a pollen-grain to escape 

 in its entirety without visible damage (unless the swelling takes place 

 too rapidly) in a few minutes. 3/N KNO3 allows this sweUing to take 

 place only slowij^, and just suflficiently in the stronger solution to cause 

 rupture of the envelope. In the course of 40 minutes coagulation has 

 set in. Similarly, 1/N HCl will first cause swelhng (due to the initial 

 diffusion of acid) and then coagulation, the intine being burst and the 

 coagulum being more or less extruded in an irregular stream. In the 

 presence of 3/N KNO3, the swelling is sufficient only to burst the extine^ 



^These remarks apply to the cytoplasm of the vegetative cell, to which only attention has been 

 paid till the present moment. 



^Alkanet in alcohol-water, with minimum alcohol, was the reagent used. 



'This view had occurred to Mr. E. E. Free at the time of a conversation with him during the 

 progress of this work. 



