BOOK II. 
GENERAL CONSIDERATIONS. 
243 
downwards to become root ; and a leaf is emitted from the 
side of the colhim. This first leaf is succeeded by another 
facing it, and arising from its axil ; the second produces a 
third facing it, and arising also from its axil ; and, in this 
manner, the production of leaves continues, until the plant, if 
caulescent, is ready to produce its stem. Up to this period 
no stem having been formed, it has necessarily happened that 
the bases of the leaves hitherto produced have been all upon 
the same plane; and as each has been produced from the 
bosom of the other without any such intervening space as 
occurs in dicotyledonous plants, it would be impossible for the 
matter of wood, if any was formed, to be sent downwards 
around the circumference of the plant : it would, on the con- 
trary, have been necessarily deposited in the centre. In point 
of fact, however, no deposit of wood like that of dicotyledons 
takes place, either now or hereafter. The union of the bases 
of the leaves has formed a fleshy stock, cormus, or plate, 
which, if examined, will be found to consist of a mass of 
cellular tissue, traversed by perpendicular and horizontal 
bundles of vascular and woody tissue, taking their origin in 
the veins of the leaves, of which they are manifest prolong- 
ations downwards; and there is no trace of bark, medullary 
rays, or central pith : the whole body being a mass of pith, 
woody and vascular tissue, mixed together. To understand 
this formation yet more clearly, consider for a moment the 
internal structure of the petiole of a dicotyledon : it is com- 
posed of a bundle or bundles of vascular tissue encased in 
woody fibre, surrounded on all sides with pith, or, which is 
the same thing, parenchyma. Now suppose a number of 
these petioles to be separated from their blades, and to be tied 
in a bunch parallel with each other, and, by lateral pressure, 
to be squeezed so closely together that their surfaces touch 
each other accurately, except at the circumference of the 
bunch. If a transverse section of these be made, it will 
exhibit the same mixture of bundles of woody tissue and par- 
enchyma, and the same absence of distinction between pith, 
wood, and bark, which has been noticed in the cormus, or 
plate, of monocotyledons. 
As soon as the plate has arrived at the necessary diameter 
R 2 
