BRIEFER ARMGU2 es 
PHYSIOLOGICAL NOTES. II. 
(WITH THREE FIGURES) 
3. An artificial endodermis cell. 
Since the osmotic pressure depends upon the impermeability of 
the “‘semi-permeable” membrane to the solute, it is possible for the 
osmotically active matter in a cell to exert a different pressure in 
different directions if the protoplasm is permeable to it in different 
degree in different parts; and by exerting different pressures it should, 
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Fic. 1. 
take up water where the 
it off where the pressure is 
though its clearness may 
when in a state of complete turgescence, 
Semi-permeability is most perfect, and pass 
least. This is generally accepted theory, 
depend somewhat on the reason given for the entrance of the water, 
but its soundness has not hitherto, so far as I know, been demonstrated 
€xperimentally. This may be done as follows: over two ends of , T 
tube 4, tie parchment paper; soak one of these ends thoroughly in a 
Solution of K,Fe(CN),; seal both ends into glass tubes, 2, C, with 
Communicating tubes, D, £, bent at right angles, fill the tubes C 
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