O. N. Purvis 



363 



4m 



a/x 



Maylfc. 51. Juoeg. IS. 5L6. 



Fig. 18. Mean thickness of walls, sclerenchyma, in presence of added nitrogen. 



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

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



May16 31 June 8 15 Z6 



Fig. 19. Mean diameter of lumina, sclerenchyma, in presence of added nitrogen. 



Full line — Plot 9, with added potassium salts. 

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



