42° THE VEGETABLE WORLD. 
unfit for the uses to which cork is destined. It is necessary, 
therefore, to strip it off before it acquires this hard and fissured 
appearance. 
Barking or peeling off the suber of the Cork-oak dose no injury 
to the tree, it is so managed as to avoid injury to the newly 
formed suberous layer, and consequently to the living and under- 
lying layers of the bark. The operation is usually performed when 
the trees have attained the circumference of ten or twelve inches. 
The process is performed during the summer months, by cutting a 
longitudinal notch in the trunk of the tree, intersecting it with 
several transverse incisions distant about forty inches from one 
another. The bark is then beat in order to break away the 
adhesion of the cork to the living layers, and separate the under- 
lying tissues. The bark is then detached in the shape of cylin- 
drical pieces, by means of the handle of an axe, made crooked and ~ 
thin at the end, as represented in Plate ITI. 
The Cork-tr£E is peculiar to hot countries. Algeria possesses 
several forests of this tree in course of working. Spain has long 
been celebrated for its produce. The crops of cork are generally 
gathered, in each forest, once every eight years. The suber lies 
immediately over a cellular mass of a very different nature. 
The cells which constitute this layer are polyhedral, they are 
thicker and more loosely joined, and of a greenish colour. This 
colouring is owing to the presence of Chlorop/y/l, a matter peculiar 
the green organs of vegetables, which is applied to the 
internal face of the cellular walls. Chlorophyll presents itself, in 
a mature state, under the form of very small rounded globules, 
formed of albuminous and fatty matter, sometimes enclosing small 
kernels of starch in their interior, and appearing to be super- — 
ticially penetrated by the green colouring matter. 
To these three cortical formations a fourth must be added which a | 
bears the name of /ider, and generally appears formed of rows 
composed of substances with thick and thin walls alternately. — 
The first are fibres of a brilliant white, longer and more slender 
than the ligneous fibres; their walls are very thick and are often © 4 
dotted and extremely tough. 
The fibres of /ier render an important service to human industeyy 4 
= since they furnish the materials for ropes, thread, and the strongest a 
