1885.] vegetable cells and the degeneration occurring in them. 325 



on some pathological change. Instances occur also in which cell- 

 walls of a cellulose nature when living give a definite lignin 

 reaction when dead. In lignified and suberised walls the maximum 

 change occurs in the neighbourhood of the middle lamella, and 

 here too the change is associated, although to a less degree, with 

 mucilaginous degeneration. 



In conclusion the author stated that he had undertaken the 

 above investigation mainly for the purpose of ascertaining whether 

 intercellular protoplasm was ever present, in plant tissue. All his 

 frequently repeated observations most emphatically negatived the 

 occurrence of any such substance. 



November 23, 1885. 



Professor Foster, President, in the chair. 



Mr F. J. Allen, M.A., St John's College, was elected a Fellow. 

 The following communications were made to the Society : — 



(1) On a new method of producing the fringes of interference. 

 By L. R. Wilberforce, B.A., Trinity College. 



[Abstract.] 



The author stated that in the course of an inquiry into the 

 suitability of various forms of interference-fringes for certain in- 

 vestigations on the velocity of light upon which he had been 

 engaged, he had been led to adopt the mode of production which 

 was the subject of his paper. 



He briefly described the method, indicated the elements of its 

 theory, and, by a comparison of his results with those of former 

 experimenters, shewed the great increase of accuracy attainable 

 by means of it. 



The paper is being printed in the Transactions of the Society. 



(2) Some experiments on the dielectric strength of mixtures 

 of gases. By Dr C. Olearski. Communicated by Prof. J. J. 

 Thomson. 



G. Wiedemann and Riihlmann in their investigations on the 

 passage of electricity through gases 1 compared the electric strength 

 of oxygen, nitrogen and air free from carbonic acid and aqueous 



1 Pogg. Ann. Vol. 145, S. 235, or Wiedemann Elektricitat, Vol. iv. p. -160. 



