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EXPLANATION OF THE PLATES. 237
h to c. Fibres less numerous, less thick, less compact,
and less hard.
c to d. Weak fibres at a greater distance from one another
: in the centre of each of which there is a tube which
has been filled up in the fibres a to h and b to c. The cellular
tissue is evidently more considerable in this part than
in the space b to c, and still more than in the space a to 0^
where the wood predominates.
e. The oldest fibres.
J'.
g.
The fibres of a middle age.
The youngest fibres. This arrangement shows that
the growth of the wood is entirely different from that in
the stem of dicotyledon plants.
h. Union of the woody fibres as they run along the stem.
Fig. 5. Vitis vinifera. V'm'if'erce. A vertical and diametrical
section of a young branch magnified.
a to b. Bark.
b to c. Wood.
c to d. Pith.
e. Woody fibre of the bark.
f.
g.
Medullary rays.
Cellular tissue, constituting the solid part of the wood.
h. Large porous or slit tubes.
i. A double trachea, or air vessel.
k. Cells of the pith.
/. Porous cells.