74 J- H. Priestley and Dorothy Armstead 
The basis of our method was to suck sugar solution or distilled 
water through a long piece of stem, on which all lateral branches had 
been cut off and the surfaces thus exposed sealed with wax. The 
change of concentration in the liquid after its passage through the 
stem was then noted. The method suffers from many disadvantages. 
When a liquid is drawn through a long piece of stem in this way 
some is invariably lost in transit, and on the other hand the first 
few drops withdrawn consist of liquid previously within the xylem 
vessels. Furthermore, a certain amount of sugar will diffuse from 
wounded cells at the end of the stem into the liquid being collected. 
An actual experiment showed that the latter source of error could be 
neglected, the amount being negligible in comparison with the 
quantities of sugar drawn through the xylem; and the other sources 
of error are not sufficient to vitiate the few conclusions that have 
been drawn from the results obtained. 
Figures obtained in typical experiments are now given. Table I 
shows the difference between the amounts of sugar absorbed during 
passage through living and dead stems respectively. These experi¬ 
ments probably indicate the qualitative difference that exists between 
physical adsorption of sugar by the walls of the containing tissue and 
the physiological absorption which reinforces that process in the 
living stem. 
Table I 
*3 
T 3 
*3 
gar 
<V 
bD 
a 
Mercury 
manometer 
Time 
Amount liq 
through 
Amount liq 
lost 
P 
m 
*3 
.3 
*tUD 
O 
P 
in 
m 
03 
0. 
u 
0 ) 
4 -> 
MH 
< 
13 
<t> 
X 
M 
O 
US 
XI 
< 
Absolute 
amount sug 
absorbed 
Plant 
Solution 
cms. 
hrs. 
c.c. 
c.c. 
% 
% 
0/ 
/o 
gm. 
j Sycamore living 
Mixture of 
35-49 
22 
64 
1 
3-4 
1*0 
2*4 
i -54 
cane sugar 
and glucose 
\ Sycamore dead 
Glucose 
66—70 
i 8 £ 
86 
34 
2-0 
1-5 
o -5 
0-4 
1 Elm living 
ff 
65 
22J 
145 
20 
1-9 
1-4 
0-5 
o-6 
l Elm dead 
yy 
60—66 
22j 
46 
14 
2-0 
1-8 
0-2 
0-09 
i Syringa living 
yy 
72 
24 
9 
3 
2'0 
•63 
1-37 
0-123 
1 Syringa dead 
yy 
72 
23 
4 
6 
2-0 
1-7 
0-3 
0-012 
If the removal of sugar from the dead 
stem is an 
adsorption pro- 
cess then it should be reversible. The following data for another 
experiment show that, within the limits of accuracy which the 
experimental conditions permit, the process seems to be reversible. 
