THE STEM OF PLANTS. 43 
as well as the most delicate cloths. In Fig. 49 the fibres of 
Hemp (Cannabis sativa) are shown as a common example of the 
vegetable substance known under the name of /ider. These fibres 
are joined in bundles. The bundles are arranged in concentric 
circles, frequently joined to one another by 
anostomose at the extremities, and constitute | 
very thin super-imposed layers, which appear 
like a sort of tissue, of a more or less loose 
texture. The whole of these layers together 
were formerly compared to a book, every leaf 
of which would represent a layer. Thence 
the rather unsuitable name of lider. 
The stratum having thin walls is formed 
of cells, which, in spring, enclose fecula and 
some very remarkable fibres, the very thin 
walls of which are extensively punctured and 
covered by wonderfully delicate meshes of 
network, with interstices often not more than 
suiooth part of a line in diameter. These fibres, 
whose physiological functions appear to be 
considerable, are called reticulated fibres. 
We cannot conclude our examination of 
bark without noticing the existence of a 
product which latterly has singularly occupied © 
the attention of botanists. We mean the — is-4—tiberine filres of 
latex and the /aticiferous vessels. 
In the bark and in the pith of some trees, vessels are noticed 
very different from those we have hitherto spoken of. They are 
remarkable at once for their structure and their contents. They 
are tubes simple or ramified, sometimes completely independent 
sometimes attaching themselves one to the other in a continuous 
length. While the vessels traceable in the woody fibres are formed 
of cells which can be separated one from the other by the use of 
proper means, the cells constituting the | taticgforos. vessels are, 08 
the contrary, so intimately blended together tl 
nor chemical action can separate them. 
The laticiferous vessels contain a juice, generally coloured. It 
is easily proved, under the microscope, that this liquid is composed 
