No. 633] SHORTER ARTICLES AND DISCUSSION 



367 



In a plant which has been steamed the nutrient channels are 

 the same as in a normal plant. The apical bud is growing and 

 attracting material to it so that we cannot say this food material 

 is now available for the cotyledonary buds as uv might had the 

 growing tip been actually cut off or prevented from actively 

 growing by a hydrogen atmosphere. The evidence is conclu- 

 sively against the view that growing points prevent the growth 

 of dormant bnds l>y atf racting and utilizing the nutrient material. 



It would seem that the inhibitive influence must be dependent 

 on living functioning protoplasmic connections. How are we to 

 conceive of an influence of this sort without invoking a vital istie 

 explanation? I believe the explanation lies in the direction de- 

 veloped at length with the aid of metal models by Lillie. 6 Grow- 

 ing points are of a different electrical potential as compared with 

 other points and the currents so generated passing through dor- 

 mant buds in the proper direction, prevent their growth. The 

 potentials are phase boundary or membrane potentials, possibly 

 dependent on selective ionic permeability or solubility of two 

 phases (cell and medium) to ions, and consequently dependent 

 or normal permeability conditions throughout the plant, Inter- 

 ruption of living protoplasmic connections, then, means merely 

 the interruption in continuity of semipermeable membrances in 

 longitudinal axes of the plant (vascular bundles?). While we 

 may be sure that the steamed portion of a plant will conduct an 

 electrical current, since its normal semipermeable nrnmbranes 

 have been destroyed there is no means of obtaining a return cir- 

 cuit. The plant is divided into two electrical systems instead of 

 one and behaves practically as two distinct plants. As Lillie 7 

 bas suggested the effect of gravity on the inhibitive influence of 

 growing stems, pointed out by Loeb, may be explained by move- 

 ment of sap downward and passage of a greater current through 

 this region because of increased electrical conductivity there. 

 Biological polarity thus becomes electrical polarity and a given 

 process at one region or pole is automatically accompanied by 

 the reverse process at the opposite region or pole. 



E. Newton Harvey 



Physiological Laboratory, 



Princeton University 

 « Lillie, R. S., Biol. Bull, XXXIII, 135, 1917. 



