July, 1923] 
CURTIS — EFFECT OF RINGING A STEM 
375 
very closely to those of the nitrogen determinations. There was a smaller 
absolute increase in the ash of the leaves from the ringed stems as well as 
a smaller increase per unit of area and a distinct decrease per unit of weight. 
Table 6 . The effect of ringing on the nitrogen content of the wood and hark of stems. 
Averages of seven determinations except where indicated in brackets 
Check 
Basal 20 cm. 
Ringed 
Basal 20 cm. 
Ave. 
Ratio 
Ringed 
Check 
Upper Part 
Ringed 
Upper Part 
Ave. 
Ratio 
Ringed 
Ave. 
Ratio 
Bark 
Ave. 
Ratio 
Bark 
Ave. 
Ratio 
Bark 
Ave. 
Ratio 
Bark 
Check 
Check 
Wood 
Wood 
Wood 
Wood 
Ave. dry wt. 
(6) 
( 5 ) 
( 5 ) 
wood (g.). . . 
I.4366 
1.2217 
O.827 
1.3619 
1-3465 
0-943 
Ave. dry wt. 
(6) 
(6) 
( 5 ) 
( 5 ) 
( 5 ) 
bark (g.) ... 
O.5467 
O.39I 
0.6842 
O.606 
I.24O 
0.8009 
0.647 
0.9658 
O.819 
I.24I 
Ave. total 
nitrogen, 
(6) 
( 5 ) 
( 5 ) 
wood (mg.) . 
IO.16 
5.16 
O.462 
10.34 
5.85 
0-457 
Ave. total 
nitrogen, 
(6) 
(6) 
( 4 ) 
( 4 ) 
( 4 ) 
bark (mg.).. 
8-34 
O.854 
8.05 
I.904 
O.915 
12.37 
1.387 
12.58 
2.669 
0.901 
Ave. nitrogen 
per g., 
(6) 
( 5 ) 
( 5 ) 
wood (mg.). 
7-13 
3-90 
0.545 
7-33 
3.38 
0.499 
Ave. nitrogen 
per g., 
• 
(6) 
(6) 
( 4 ) 
( 4 ) 
( 4 ) 
bark (mg.).. 
16.11 
2.25 
11.41 
3-i5 
O.738 
1543 
2.17 
11.09 
3.14 
0-747 
Ave. nitrogen 
per g. 
( 5 ) 
( 5 ) 
stem (mg.).. 
9.27 
6.69 
O.73I 
10.40 
6.87 
0.682 
The data thus far presented clearly indicate that ringing commonly 
hinders the movement of nitrogen and ash constituents into the tissues 
above the ring. This cannot be considered as conclusive evidence, how¬ 
ever, that the phloem rather than the xylem is chiefly concerned in the 
movement of these nutrients. I have obtained considerable evidence show¬ 
ing that transpiration from the leaves of the ringed stems is distinctly 
less than that from normal leaves. This is due, in part at least, to the 
high concentration of solutes above the ring with a corresponding lowering 
of vapor pressure, and perhaps also to increased retention by colloids or 
to morphological or other changes. If the nutrients are carried in the so- 
called “transpiration stream,” and if their rate of movement is determined 
by the water movement, a check in the transpiration from tissues above 
a ring would very probably reduce the movement of the solutes into these 
tissues. In order to eliminate this factor of transpiration, twigs of privet 
were experimented with as described below. 
Twelve sets of three stems each were selected for the experiment. In 
every twig the young growing shoot was removed and four pairs of leaves 
were left at the apex. The four pairs of leaves immediately below these 
