the Branches in Shrubs and Trees . 
633 
These measurements showed : — 
1. A large inward movement accompanying the fall of the leaves, and 
an outward movement accompanying the formation of new leaves. 
2. A real seasonal movement independent of leaf-fall and leaf-forma- 
tion, consisting in an inward movement during the advancing winter, and 
an outward movement on the approach of spring. 
3. Certain fluctuations in the movements, the reasons for which were 
not evident. 
The causes of the movement accompanying leaf-fall and leaf-formation 
are so evident as hardly to call for comment ; the movement is simply due 
to the removal of the weight of the leaves and their contained water from 
the elastic, obliquely-ascending branches in the one case, and the addition 
of weight in the other. But the cause of the further seasonal move- 
ment of the leafless branches is not at once evident. 
The measurements showed not only that there is a real movement of 
the leafless branches, but that it is of considerable amount, reaching 
between leaf-fail and leaf-formation — 
1 2 cm., or 5°/ o of the total diameter of the plant in Salix laurifolia ; 
3-5 cm., or over 3% of the diameter of the plant in Cercidiphyllum 
japonicmn ; 
5-3 cm., or over 5 °/ o of the diameter of the plant in Cor 7 ius Jiorida ; 
And a larger though uncertain amount in Broussonetia papyrifera. 
The results were of such interest that a more careful study of the 
subject was undertaken the following winter (1899-1900). An improve- 
ment was made in the method in two respects. First, the movement 
of each branch was measured separately in order to determine whether 
there was any difference in the movement of the different branches. 
This was effected by placing, in all measurements, the loop of the tape 
(a Chesterman steel tape as used the preceding year) over a brass screw 
held by a cork set in the top of a piece of stout gas-pipe, which was driven 
firmly into the ground as nearly as possible in the centre of the shrub (as 
represented by Fig. 53). It is important to note that this, like any other 
method of measuring such movements from a fixed point, does not give 
strictly accurate results, because the marks on the branches do not move 
in and out along the same radial line, but in different lines. In general ? 
however, the errors from this source are very slight, they tend to neutralize 
one another, and as a whole they affect the results in the direction of a 
lesser rather than a greater amount. Secondly, some suggestion having 
arisen that temperature might have an effect upon the process, the air 
temperature was recorded at each measurement. The measurements were 
made by one of my senior students, Miss Phoebe Persons, as often as the 
weather would permit, throughout the autumn, winter, and spring. One of 
the greatest difficulties in this study consists in the fact that the measure- 
