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HISTOLOGY OF VEGETABLES. 
classes of plants, each variety being characterised by the 
name of tissue ; thus we have the woody, the vas- 
cular, the porous, and other tissues. The first of these is 
the most important, since to it we are indebted for our 
linens, our cordage, and our paper. It consists of 
elongated tubes or fibres of a more or less cylindrical 
figure, and occurring in bundles ; by maceration, and 
other processes, the . fibres are detached from each other, 
and are then capable of being worked into fabrics of 
various kinds. 
The vascular tissue consists of cells more or less 
elongated, joined end to end, or overlapping each other, 
in which either a spiral fibre or a modification of the 
same has been deposited ; hence, if the spiral be perfect? 
such a vessel is called a true spiral vessel ; if inter- 
rupted at certain parts, and the fibre breaks up into a 
series of rings, it is then called annular ; if the fibre 
or rings be connected together by branching fibres, in 
such a manner that a network is produced, the vessel 
is called reticulated ; if the fibres be nearly close 
together, and the vertical connecting bands short and 
equi-distant, the vessel is called scalariform , from the 
markings resembling the rounds of a ladder. Spiral 
vessels, from their resemblance to the air-tubes of 
insects, have been termed Trachea by some authors ; 
the analogy, however, is not far fetched, as in both 
cases, the tubes are composed of a transparent mem- 
brane, kept open by a spiral fibre. 
In all the above- described vessels the spiral fibre has 
