ELASTIC SUBSTANCE ON SHOOTS AND YOUNG LEAVES. 135 
both within and without the shoot, giving it considerable 
strength. A very young shoot could often be stretched 
half an inch or more before breaking. The undeveloped 
leaves of the shoot are completely covered with the sub- 
stance in their earliest stage, while they are quite green. 
As the minute and closely folded leaves of the shoots 
expand, and thus form separate leaves, they soon become 
bright red in colour, and in this early stage are still coated 
with the elastic substance, which also gives them a very 
glossy appearance, particularly on the upper surface. As 
the leaves grow larger the elastic substance quickly 
changes, and a stage is soon reached when it is difficult to 
detect any of it remaining on the leaf, particularly after 
the third small one from the end of the branchlet. 
The substance is less pronounced on the under than on 
the upper side of the leaf, although in the earliest stages 
it covers the whole of it, as well as the petiole. The sub- 
stance can often be entirely stripped from the upper surface 
of the very young leaves, thus proving that it is only a 
surface coating.- It cannot be thus easily removed from 
the underside of the leaf, where the coating soon becomes 
very thin and difficult to detect, except on the midrib and 
around the edges. The changes which quickly take place 
seem thus to be more rapid on the underside of the leaf, 
and the varnish-like appearance of the young leaves soon 
disappears, the surface becoming quite dull. 
Although the unfolded shoot consists so largely of this 
elastic substance, yet the coatings of the leaves are dis- 
tinct in their earliest stage, and expand with them as they 
grow. To prevent them adhering together at this stage, 
their surfaces are coated with a white powdery resinous 
or waxy-like substance, which is very soluble in ether, and 
by which means its presence can readily be determined. 
