“A glance of the eye, thrown on the section of a log of wood destined for warming, permits us to recognize that the tige of the trees of our forests presents three essential parts, which are, in going from within to without, the pith, the wood, and the bark.  The pith, (in French, marrow,) forms a sort of column in the centre of the woody axis.  In very thick and old stems its diameter appears very little; and it has even for a long time been supposed that the marrow ends by disappearing altogether from the stems of old trees.  But it does nothing of the sort;[37] and it is now ascertained, by exact measures, that its diameter remains sensibly invariable[38] from the moment when the young woody axis begins to consolidate itself, to the epoch of its most complete development.”

So far, so good; but what does he mean by the complete development of the young woody axis?  When does the axis become ‘wooden,’ and how far up the tree does he call it an axis?  If the stem divides into three branches, which is the axis?  And is the pith in the trunk no thicker than in each branch?

9.  He proceeds to tell us, “The marrow is formed by a reunion of cells.”—­Yes, and so is Newgate, and so was the Bastille.  But what does it matter whether the marrow is made of a reunion of cells, or cellars, or walls, or floors, or ceilings?  I want to know what’s the use of it? why doesn’t it grow bigger with the rest of the tree? when does the tree ‘consolidate itself’? when is it finally consolidated? and how can there be always marrow in it when the weary frame of its age remains a mere scarred tower of war with the elements, full of dust and bats?

[Illustration:  FIG. 24.]

‘He will tell you if only you go on patiently,’ thinks the reader.  He will not!  Once your modern botanist gets into cells, he stays in them.  Hear how he goes on!—­“This cell is a sort of sack; this sack is completely closed; sometimes it is empty, sometimes it”—­is full?—­no, that would be unscientific simplicity:  sometimes it “conceals a matter in its interior.”  “The marrow of young trees, such as it is represented in Figure 24 (Figuier, Figs. 38, 39, p. 42), is nothing else”—­(indeed!)—­“than an aggregation of cells, which, first of spherical form, have become polyhedric by their increase and mutual compression.”

10.  Now these figures, 38 and 39, which profess to represent this change, show us sixteen oval cells, such as at A, (Fig. 24) enlarged into thirteen larger, and flattish, hexagons!—­B, placed at a totally different angle.

And before I can give you the figure revised with any available accuracy, I must know why or how the cells are enlarged, and in what direction.

Do their walls lengthen laterally when they are empty, or does the ‘matiere’ inside stuff them more out, (itself increased from what sources?) when they are full?  In either case, during this change from circle to hexagon, is the marrow getting thicker without getting longer?  If so, the change in the angle of the cells is intentional, and probably is so; but the number of cells should have been the same:  and further, the term ‘hexagonal’ can only be applied to the section of a tubular cell, as in honeycomb, so that the floor and ceiling of our pith cell are left undescribed.