102 
OTIS F. CURTIS 
through the phloem? And (2) Is there normally an upward movement of 
this food from the roots and lower trunk to the growing shoot? The 
present discussion will deal with the former question; the second question 
will be discussed in a subsequent paper. 
Effect of Ringing on Growth of Leafy and Defoliated Shoots. 
Vigorous young shoots of PMladelphus puhescens Loisel. were treated 
on May 30 as indicated in table i. In this as in subsequent tables those 
shoots having the same letter were fairly well matched as to size, vigor, and 
position on parent plant. 
Table i. Philadelphus puhescens. Rings in new growth 15-20 cm. from tip. Stems 
measured from attachment to main stem. May jo to June 8, igi8 
Not Ringed. Leaves 
Remaining 
2 
Ringed 15-20 Cm. from 
Tip. Leaves Re- 
maining 
3 
Not Ringed. Leaves 
Removed from Upper 
15-20 Cm. 
4 
Ringed 15-20 Cm. from 
Tip. Leaves Above 
Ring Removed 
Length 
in Cm. 
May 30 
Length 
in Cm. 
June 8 
Gain in 
Cm. 
Length 
in Cm. 
May 30 
Length 
in Cm. 
June 8 
Gain in 
Cm. 
Length 
in Cm. 
May 30 
Length 
in Cm. 
Junes 
Gain in 
Cm. 
Length 
in Cm. 
May 30 
Length 
in Cm. 
Junes 
Gain in 
Cm. 
a . . . 
b. ... 
c. . .. 
d. ... 
e . . . . 
52.5 
58.0 
49-5 
54-0 
59.0 
81.5 
79-5 
85.0 
90.0 
99.0 
28.5 
21.5 
35-5 
45-0 
40.0 
61.0 
60.0 
78.0 
61.0 
59-0 
79.0 
75.0 
Broken 
67.0 
67.0 
18.0 
15.0 
6.0 
8.0 
40.0 
53-5 
40.5 
64.0 
60.0 
69.0 
85.0 
66.0 
92.5 
80.5 
29.0 
31.5 
25-5 
28.5 
20.5 
58.5 
60.5 
63.5 
55.0 
58.0 
58.5 
61.5 
81.5 
55-5 
80.0 
0.0 
I.O 
I8.0I 
0.5 
22.0^ 
Avera 
ge gain 
34.1 
11-75 
27.0 
0.5 
The measurements of June 8 show very clearly that ringing has in some 
way checked the growth of the shoots. The simplest explanation appears 
to be that the food necessary for shoot formation passes upward through 
the phloem and not through the xylem tissues. The few leaves present 
above the ring (group 2) are able to synthesize sufficient food to allow for 
some growth. In two shoots of group 4 a narrow strip of phloem was left 
by accident, and this has served to transfer sufficient food to allow for con- 
siderable growth. Two or three small leaves unfolded at the apex of the 
stems of group 4, but these were too small to carry on much photosynthesis, 
so growth continued very slowly for several weeks until other leaves had 
developed. 
The same experiment was repeated with Philadelphus in the spring of 
1919, except that in this case, instead of making the ring in the upper part 
of the new growth, the ringing was done on the wood of the previous year 
just below the bases of the young shoots. As the stems had been cut back 
when dormant, this left the new shoots at the apex of the stem. In each 
case, whether the leaves were or were not removed, one pair of leaves 
enclosing the growing tip was removed. The measurements are recorded 
in table 2, and a photograph of those shoots lettered g is shown in figure i. 
1 Not included in average. A strip of phloem was left on about % of the circumference. 
The twig was bent at an angle at this point. 
