1917] BROOKS—PERMEABILITY 245 
solution, the resulting osmotic pressure will be considerably above 
that of a similar mixed solution (that is, one just insufficient to 
cause plasmolysis), and plasmolysis will result. 
Summary 
From a consideration of the methods heretofore used in the 
study of permeability it would appear that the steps most essential 
to further progress toward the solution of the problem are: (1) a 
‘thorough analysis of the various disturbing factors in the methods 
involving chemical determinations and the satisfactory interpreta- 
tion of the results secured by such methods; (2) the same type of 
analysis of the methods depending on turgor, with special reference 
to the Reon effect of emanate and (3) the establishment of 
methods of d in ee without — 
the various disadvantages of the other methods. 
The writer hopes to show in subsequent papers that the dif- 
fusion method, which he has devised, answers these requirements, 
and that it is also possible to interpret satisfactorily the data 
obtained by certain methods dependent upon the use of turgorasa 
criterion. e oe 
LABORATORY OF PLANT PHYSIOLOGY 
VARD Universrry 
eed jad pecan ‘Gai. Jour. Micr. Sti. sacs 1883. ee 
a renee S. pica A study of permeability by the method of ‘tissue ten- 
sion. Amer. Jour. Bot. 10: 562. T916. a ee a 
