Tap water +12.4 



0.1 M + 6.5 



0.2 + 3.4 



0.3 + 0.8 



0.4 — 9.6 



0.5 —19.5* 



0.6 —21.9 



0.7 —27.6 



0.8 —33.0 



1.0 —33.6 



* AH cells plasmolyzed at this point. 



when permitted to swell or to shrink. Especially is this true of epidermis 

 with its cuticle on one side. That of Sedum nicaense has been shown to 

 decrease in the two surface dimensions upon swelling (increase in total 

 volume) in water. Table 26 shows the measurements. 



Table 26. — Changes in dimensions of epidermal strips from Sedum nicaense leaves. 

 Values are arbitrary units (Currier, 1943) : — 



L = Length; W = Width; D = Depth or thickness. 



The simplified method may theoretically be extended to measurement 

 of all three osmotic quantities in the following manner. Letting O = 

 osmotic pressure of the tissue, DPD =: diffusion pressure deficit of water 

 in the tissue, T = turgor pressure of the tissue, V = volume of the tissue, 

 and the subscripts g = limiting plasmolysis, n := normal state, and s ^ 

 water saturation, the following relations should be valid. 



Og = OP of plasmolyticum causing minimum volume {13) 



On = Og • -^ {14) 



Vn 



Os = Og • 4^ {15) 



Vs 



DPDg = Og {16) 



DPDn ^ On — Tn = OP of plasmolyticum causing no change in Vn {17) 



DPDs = zero {18) 



Tg = zero {19) 



Tn = Ts • ^^'" — Vg^ = On - DPDn {20) 



(Vs — Vg) 



Ts = Os {21) 



This method proves convenient for rapid estimation of approximate 

 values for these states of a given tissue. 



