92 Keeble. — The Hanging Foliage of 
to be rendered doubtful ; and, in conclusion, to put forward 
a somewhat more extended view of the significance of this 
hanging habit. From the observations of the destruction 
of chlorophyll, of the rates of transpiration, of the shade- 
loving habits of the trees, it cannot, I think, be doubted that 
the young leaves are protected by their hanging position. 
But in addition to this temporary advantage I would suggest 
an additional permanent advantage — permanent in the sense 
that its benefit is felt throughout the life of the branch. 
Beside affording protection to the young foliage, by this habit 
the branch and its pendent petioles are able to wait in a safe 
position till the conditions of shade or sun, as far as they 
are determined by the disposition of the young branches of 
other shoots, can, to use a figure of speech, be ascertained. 
At all events, during this delay, a step toward the permanent 
condition of light or shade is being made by the adjustment 
of other shoots ; so that, on rising up, the branch with its 
leaves meets conditions more akin to those under which it 
must live than if it had pushed its way horizontally. But 
still more important is the fact that the pinnate leaves have 
a far greater range of positions which they can adopt than 
if they had grown in the normal way, obliquely outward, 
their basal parts becoming rapidly rigid, so that only their 
growing apical parts could adjust themselves to changing 
conditions of insolation. The petiole has, on rising, the power 
of assuming any position, from one pointing almost vertically 
downward to one pointing upward. Such a power of re- 
sponding to differences of external conditions could not exist 
in a petiole which arose at a certain definite angle with the 
stem, and whose basal part became rapidly rigid. 
By means of the ‘ waiting ’ and the rising up of the 
branch and the petiole, the shoot may be likened in its 
behaviour to one of the leaflets borne by the petiole : both 
adjust themselves to a nicety to the prevailing conditions of 
insolation. 
To state the case in another way : the two movements 
of the shoot with its leaf and of the leaflets may be likened 
