A Theory of Geotropism. 63 
10. Henderson, L. J. and Cohn, E. J. On the swelling of protein colloids. 
Jour. Amer. Chem. Soc., 40, p. 857, 1918. (Fischer’s 
reply, ibid p. 862; Henderson’s counter reply, ibid 
p. 867). 
11. Lillie R. C. The Role of Membranes in Cell Processes. Pop. Sci. 
Monthly, 82, p. 132, 1913. 
12. McClendon, J. F. Physical Chemistry of Vital Phenomena. Princeton 
Univ. Press, 1917. 
13. Mobius, M. Movements of orientation in buds, flowers and fruits. Flora, 
111-112, p. 396, 1918. 
14. Newcombe, F. C. Geotropic response at various angles of inclination. 
Ann. Hot., XIX, p. 311, 1905. 
15. Perrin, J. Brownian Movement and Molecular Reality. Eng. trans. 
London, 1910, 
16. Price, S. R. Some Studies on the Structure of the Plant Cell by the 
Method of Dark-ground Illumination. Ann. Bot., 
XXVIII, p. 601, 1914. 
17. Roon, L. and Oesper, R. E. Theory of Emulsification based on 
Pharmaceutical Practice. J. Ind. Eng. Chem., 
9, p. 156, 1917. 
18. Small, J. Geotropism and the Weber Law. Ann. Bot., XXXI, p. 313 
1917. 
19. „ ,, Changes of Electrical Conductivity under Geotropic 
Stimulation. Proc. Roy. Soc. Lond., B. 90, p. 349, 
1918. 
20. ,, ,, Origin and Development of the Composite, New Phytologist 
Rep. XL, 1919. 
-21. Stiles, W. and Jorgensen, I. The effect of Temperature on the 
Permeability of Plant Cells to the Hydrogen Ion. 
Ann. Bot., XXIX, p. 611, 1915. 
22. Stiles, W. Irritability. Science Progress, Vol. XIII, No. 51, p. 395, 1919. 
23. Tolman, R. C. and Stearn, A. E. The Molecular Mechanism of 
Colloidal Behaviour. I. The swelling of fibrin in 
acids. Jour. Amer. Chem. Soc., 40, p. 264, 1918. 
24. Waller, A. D. Points relating to the Weber-Fechner Law. Brain, 1895, 
p. 205. 
25. ,, ,, The Signs of Life. London, 1903. 
