O. N. Purvis 



365 



35^ 



3^ 



May SI June« \S X6 



Fig. 22. Mean diameter of lumina, xyleni, in presence of added nitrogen. 



Full line ^-^ Plot 9, with added potassium salts. 

 Broken line - - - Plot 10, without added potassium salts. 



7.0 



15 



Fig. 23. 



May 51 June 8 13 Z6 



Mean ratio of lumen diameter to wall thickne.ss, in presence of added nitrogen. 



Full line ^^— Plot 9, with added potassium salts. 

 Broken line - - - Plot 10, without added potassium salts. 



{Received May 13//*, 1919.) 



