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, 

 v/oody 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 nmnber of 

 these petioles to be separated from their blades, and to be ti^ 

 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 

 bvuicli. 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 



