present in Pellia epiphylla , {Li) Cor da. 487 
siderable quantity of starch present in the thallus before the action of the 
fungus does not support this view. 
3 . The pH value of soil upon which Pellia was growing was found to 
be slightly acid. 
4 . Notwithstanding the constant occurrence of the fungus in the liver¬ 
wort, symbiosis is not obligate, as plants of the liverwort have been grown 
without the fungus. 
My thanks are due to Mr. C. T. Gimingham for information regarding 
the displacement method of obtaining soil solutions ; to Mr. C. Hunter for 
much valuable help and advice ; and to Professor O. V. Darbishire for his 
interest in the work. 
During the progress of this investigation I have been in the receipt of 
a maintenance grant from the Department of Scientific and Industrial 
Research. 
Cryptogamic Research Laboratory, 
University of Bristol, 
November 1932. 
References. 
1 . Bernard, N.: L’fvolution dans la Symbiose. Ann. des Sci. Nat., Bot., 9 e serie, ix, 1909, 
p. 1. 
2 . —-: Les Mycorhizes des Solanum. Ibid., 9 e serie, xiv, 1911, p. 235. 
3 . Cavers, F. : Gola’s Osmotic Theory of Edaphism. Journal of Ecology, vol. ii, 1914, p. 209. 
4 . Gillespie, L. J., and Hurst, L. A. : Hydrogen-ion Concentration Measurements of Soils of 
two Types : Caribou Loam and Washburn Loam. Soil Science, vol. iv, 1917, p. 311. 
5 . Magrou, J. : Symbiose et Tuberisation. Ann. des Sci. Nat., Bot., io e serie, iii, 1921, p. 1S1. 
6. Ridler, W. F. F. : The Fungus present in Pellia epiphylla. Ann. of Bot., vol. xxxvi> 
! 922 , P- 193 . 
7 . Servettaz, C.: Developpement et la nutrition des Mousses en milieux sterilises. Ann. des 
Sci. Nat., Bot., 9 e s&rie, xvii, 1913, p. hi. 
8. Stahl, E. : Der Sinn der Mycorhizenbildung. Jahrb. fur wissenschaft. Bot., xxxiv, 1900, 
P- 539 - 
9 . Wisselingh, C. van : Mikrochemische Untersuchungen iiber die Zellwande der Fungi. 
Ibid., xxxi, 1898, p. 619. 
