1915] OSTERHOUT—PERMEABILITY 253 
Summary 
Results obtained by the use of quantitative methods prove that 
the permeability of protoplasm may be greatly increased or dimin- 
ished without injury. A rapid alternation of increase (amounting 
to 20 per cent above normal) and decrease (amounting to 39 per 
cent below normal) did not produce injury. 
LABORATORY OF PLANT PHYSIOLOGY 
Harvarp UNIVERSITY 
