290 



A NOTE OF ADSORPTION 



[CH. 



separates the green protoplasm from the cell-sap), there is a very 

 large accumulation precisely at the point where the tension of the 

 originally cyUndrical cell is weakening to produce the bulge. 

 But in a still later stage, when the boundary between the two 

 conjugating cells is lost and the cytoplasm of the two cells becomes 

 fused together, then the signs of potassic concentration quickly 

 disappear, the salt becoming generally diffused through the now 

 symmetrical and spherical "zygospore." 



i^^^ 



Fig. 98. Adsorptive concentration of potassium salts in (1) cell of Pleurocarpus 

 about to conjugate; (2) conjugating cells of Mesocarpus; (3) sprouting spores 

 oi Equisetum. (After Macallum.) 



In a spore of Equisetum (Fig. 98, 3), while it is still a single cell, 

 no localised concentration of potassium is to be discerned ; but as 

 soon as the spore has divided, by an internal partition, into two 

 cells, the potassium salt is found to be concentrated in the smaller 

 one, and especially towards its outer wall, which is marked by a 

 pronounced convexity. And as this convexity (which corresponds 

 to one pole of the now asymmetrical, or quasi-ellipsoidal spore) 

 grows out into the root-hair, the potassium salt accompanies its 

 growth, and is concentrated under its wall. The concentration is. 



