Physiological Studies in Plant Anatomy 75 
Stem of Syringa vulgaris 
L. killed by steam. 
Irrigated with distilled water 
Hexose 
Absolute 
sugar 
amount 
% 
gm. 
First fraction collected 0-4 
0-03 (released by stem) 
Second fraction collected 0-15 
0-02 ,, ,, 
Irrigated with 2 % glucose 
i *5 
o-6 (retained in stem) 
Irrigated with distilled water again. 
First fraction ... ... 1-2 
0*2 (released by stem) 
Second ,, ... ... i-o 
O’ 12 
Third „ ... ... 0-3 
o-oi 
In no case was there any increase in reducing power after inversion. 
But physiological absorption represents a process of diffusion 
through a plasma membrane and this again may be expected to be 
a reversible process and dependent upon the concentration of the 
sap within and without the protoplast. 
The data given in Table II show that when distilled water is 
drawn through living stems sugar is released into the ascending 
stream and that if a current of sugar solution be substituted then 
the reverse action takes place and a certain proportion of the sugar 
is removed in passage. 
Table II 
Stems (of Msculus hippocastanum L.) irrigated with water 
Change 
Absolute 
Mercury 
Duration 
Volume 
Hexose in 
gain or 
mano¬ 
of irriga¬ 
liquid 
Volume after concen- 
loss 
Condition 
meter 
tion 
through 
lost 
irrigation tration 
hexose 
cms. 
hrs. 
c.c. 
c.c. 
% % 
gm. 
I. 
Buds opened 
58 
9 
37 
38 
O’l +o-i 
+0-04 
II. 
In leaf 
50 
H 
i 75 
35 
0-0006* +0-0006* 
(practically '* 
+ 0-001* 
nil) 
Same stems irrigated subsequently with 
2 % glucose solution 
I. 
Buds opened 
70 
5 i 
3 i 
9 
0-16 —1-84 
- 0*57 
II. 
In leaf 
7 o 
4 i 
41 
9 
0-56 — 1*44 
-o -59 
* This liquid after inversion showed 0-04 % cane sugar present or 0*07 gm. absolute amount. 
These data suggested that if it was desired to state quantitatively 
the conditions existing in the vascular strand at any particular time 
with reference to the absorption or release of sugar, this could best 
be done by finding approximately the concentration of sugar solution 
with which the protoplasts of the surrounding tissues seem to be in 
equilibrium. This concentration of sugar should suffer neither ap¬ 
preciable loss nor increase during its passage through the stem. In 
