494 BOTANICAL GAZETTE [JUNE 
in the cell sap. Nor is it likely that the lower swelling in acid 
solution is to be accounted for on the ground of osmotic pressure 
difference. The data in table II will give some idea of the réle of 
osmotic pressure in water imbibition in this plant. The figures 
% INCRLASK 
50 
Bg, Nadh 
4 Noreit.nt Sotution 
= DISTILLED WATER 
a Be, t1Ct. 
4 ty Mauic Aci 
a Dy HCL. 
Pit 
pees: 
\ 
it 
| 
\ 
N 
oO 
aj Se Hs Wd SG 
iy BS A 
\ 
BOS te RRR Bw al 
Pei i ie 
Lit 
| 
Time In Mours 
24 
Fic. 2.—Hydratation of Opuntia Blakeana 
given are for four pieces of Opuntia Blakeana in each solution, similar 
to those used in the hydratation experiments 
As may be seen, the swelling in distilled water and.N /50 KNOs 
is practically the same, the slightly higher osmotic pressure of the 
latter being without measurable effect as regards increase in weight 
