460 



A NOTE ON ADSORPTION 



[CH. 



K-ioris reach and occupy the adsorbing surfaces of the cell-membranes 

 out of all proportion to their abundance in the external media*. 

 And we may take it also that our potassium salts, hke inorganic 

 substances in general, tend to raise the surface-tension, and will be 

 found concentrated, therefore, at a portion of the surface where the 

 tension is weakf. , 



iM2^ 



Fig. 150. Adsorptive concentration of potassium salts in (1) a cell of Pleurocarpus 

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

 of Equisetum. After Macallum. 



In Professor Macallum's figure (Fig. 150, 1) of the little green 

 alga Pleurocarpus , we see that one side of the cell is beginning to 

 bulge out in a wide convexity. This bulge is, in the first place, 

 a sign of weakened surface-tension on one side of the cell, which as 

 a whole had hitherto been a symmetrical cylinder; in the second 

 place, we see that the bulging area corresponds to the position of 

 a great concentration of the potassium salt; while in the third place, 



* Cf. A. B. Macallum, Address to Section I, Brit. Ass. 1910; Oberflachen- 

 spannung und Lebenserscheinungen, in Asher-Spiro's Ergehnisse der Physiologie, 

 XI, pp. 598-688, 1911; also his important paper on Tonic mobility as a factor in 

 influencing the distribution of potassium in living matter, Proc. R.S. (B), civ, 

 pp. 440-458, 1929; cf. E. F. Burton, Trans. Faraday Soc. xxvi, p. 677, 1930. 

 • t Ii^ accordance with the "principle of Le Chatelier," which is in fact a corollary 

 to the Gibbs-Thomson Law. 



