636 Ganong. — An Undescrihed Thermometric Movement of 
ments can be made, especially when any of the leaves are on, only in 
perfectly still weather ; and hence a continuous study of the movement in 
exact correlation with external physical conditions is well-nigh impossible. 
Doubtless shelters could be devised to permit measurements in any 
weather, but with large plants this would be a matter of much difficulty, 
and it was not attempted by us. 
The shrubs studied during the winter were the seven listed in the 
table below. The results of the measurements of all seven were, except for 
minor differences, very similar, and they are fully illustrated by the two 
examples plotted on Fig. 55, which represents the movement for Linder a 
Benzoin , an average representative of the series, and Salix laurifolia , which 
was one of the two which showed the greatest movement of them all. The 
total amplitude of the movement between leaf-fall and leaf-formation for 
all the branches, and the percentage which this movement is of the shrub 
radius, are shown by the following table : — 
Plant. 
Size in 
metres . 
Movement in centimetres . 
Percentage movement. 
ht. diam. 
N. 
S. 
E. 
W. 
Av. 
N. 
S. 
E. 
W. 
Av. 
Pyrus americana . . . 
1.90 x 1-20 
2-3 
i -4 
37 
1.4 
2*20 
03 
02 
°7 
02 
3-5 
Salix laurifolia .... 
4.50 x 3.10 
11. 2 
6.0 
9-4 
8.0 
8.65 
12 
09 
10 
09 
10 
Cornus sericea .... 
2-20 X I-gO 
5.0 
5-6 
4-9 
47 
5-°5 
07 
05 
04 
05 
5-2 
Cercidiphyllum japonicum 
2-8o X 1-40 
5.2 
2.8 
3-9 
3? 
375 
13 
02 
07 
02 
6.0 
Cornus Jlorida .... 
2.30 X 1-90 
5-5 
2-5 
7-9 
5-9 
5*45 
05 
03 
07 
03 
4-5 
Linder a Benzoin . . . 
I-6o X 1-20 
3 - 1 
5'4 
8.1 
4-5 
5-27 
09 
06 
12 
06 
8.2 
Carpinus carolinianus 
2.30 X 2*00 
8.4 
9*5 
8.7 
9-5 
9.02 
11 
07 
07 
07 
8.0 
40.7 
33*2 
46.6 
37.1 
60 
34 
54 
34 
5.8 
47 
6-6 
5-3 
8.5 
4.8 
J>* 
4.8 
Further, in order to determine the effect of fluctuations of temperature 
through a single day, and the effect of the fall of temperature at. night, 
Miss Persons made, after several unsuccessful attempts, a series of measure- 
ments through one still day and part of the next, and found that within the 
limits of a single day and night the movement was considerable, and that 
it was correlated with the temperature changes, though lagging somewhat 
behind the latter. Another series of measurements made by her was 
directed to determine whether the movement was most pronounced in the 
younger or older parts of the branches, and she found, as was to be 
expected, that it was much more marked in the young parts. In general 
the movement is greatest in the longest, most slender, and youngest 
branches, and it becomes less with the reverse of those features. Miss 
Persons also made a detailed study of the anatomy of the stems she 
measured, but she was unable, as I have been since, to connect the move- 
ment with any peculiarities of anatomical structure. 
