228 F. J. Lewis and G. M. Tuttle 
Table I 
Conduc- 
tivity 
Water 
Vis¬ 
xio 6 corr. 
content 
Date 
A 
P 
cosity 
for vise. 
0/ 
/o 
Condition of cells 
Mar. 9 
1-560 
18-76 
2-0 
1006 
55-o 
Winter condition 
„ 12 
1-820 
21-88 
2-2 
675 
54*7 
,, ,, 
15 
1-701 
20-45 
3-0 
1083 
51*3 
,, ,, 
,. 22 
1-725 
20-74 
3-0 
1044 
— 
,, ,, 
» 27 
1-858 
22-34 
2-48 
897 
— 
,, >> 
April 1 
1-830 
22-00 
3-0 
1050 
— 
>7 > t 
„ 6 
1-777 
2I-36 
2-5 
867 
53-i 
Minute quantities of starch 
.. 7 
1-887 
22-67 
3-3 
1072 
49*3 
,, ,, ,, 
„ 13 
1-781 
21-66 
2-76 
816 
48-7 
,, „ ,, 
» 17 
1-797 
21-59 
3-30 
917 
— 
Increased quantity of starch. 
Contents of cell still localised 
„ 29 
1-380 
16-60 
2-64 
844 
60-4 
Larger amount of starch. 
Cells in summer condition 
May 6 
1-493 
17-96 
2-70 
852 
51-0 
As on April 29 
The atmospheric pressure P is the value corresponding to the 
observed A given in the tables published by Harris and Gortner( 3 ). 
As regards the osmotic pressures it will be observed that after 
maintaining a remarkable uniformity, a decided drop occurred at 
the time the cells began to pass into the summer condition. A 
marked drop in the total sugars in the sap was recorded in 1919 at 
this time (2), but a partial recovery both in osmotic pressure and 
sugar content appears to take place at the beginning of summer. 
The water content of the tissues may be partly responsible for 
the change in pressure, but the evidence for this is not conclusive. 
The water content appears generally to diminish during late winter 
and rise again when photosynthesis and transpiration become active. 
But material fluctuations occur for which light and temperature may 
be responsible; for example, on April 7 and 13 the water content 
was 49-3 and 48-7 respectively. This was during a period of moderate 
warmth when the day temperature varied between 40° to 55 0 F., 
whilst the night temperature dropped to about 20° F. and the cells 
were already in the state of change from winter to summer con¬ 
dition. On April 29 the water content had risen to 60*4 per cent. 
This was during a warm period when both absorption from the soil 
and transpiration were exceedingly active. The drop to 51 per cent, 
on May 6 was probably due to excessive transpiration, as daily 
temperatures of 70° F. were then recorded, with a hot dry wind. 
The viscosity of the sap varies from 2*5 to 4 at different periods. 
Thus a considerable correction has to be applied to the conductivity. 
