84 Gibson . — Contributions towards a Knowledge of 
in the plane at right angles to the ridge. Fig. 1 shows the 
earliest distinctly recognizable stage in the development, the 
left-hand side of the figure representing the surface of the stem, 
whilst the leaf-face is partly shown on the right. The ridge 
is shown here as three cells broad, and these cells may be 
distinguished very early, not only by their greater size, bulg- 
ing out into the angle between the leaf and the stem, but also 
by the fact that they take on a deeper stain than do the 
surrounding cells, and have larger nuclei. At the margins 
the ridge is only one cell broad. These cells speedily undergo 
transverse division, so that a basal sheath of cubical cells 
(Figs. 2, 3, and 4) is formed continuous with the epidermis of 
the leaf and stem, the free segments growing outwards to form 
the ligule itself. The sheath-cells may undergo further divi- 
sions, as shown in Figs. 3 and 6, and the cells of which it is 
composed at a later date become thick-walled and cuticu- 
larized. The next layer of cells from the merismatic pro- 
minence gives rise to the glossopodium ; these cells enlarge 
greatly, and do not stain so deeply as the sheathing-cells or 
those of the body of the ligule, whilst the general cells of the 
body of the ligule remain as a rule of much smaller size. 
The ligule has "completed its development long before the 
leaf to which it belongs ; indeed, it has reached its adult size 
and shape at a distance of from 1 to ij mm. from the apex of 
the shoot. Occasionally the clearer basal cell-layer or glos- 
sopodium becomes four cells broad (Fig. 6 ), but three is by far 
the commoner number. The body of the ligule itself may, 
however, be six or even more cells thick. Fig. 5 shows 
a transverse section of the ligule in a comparatively young 
condition, while in Fig. 6 a longitudinal section of an adult 
ligule shows it to be composed of five cell-rows. 
.S. Martensii. Pfefifer (/. cl) describes the ligule of S. Mar- 
ten si i as arising from one row of from four to six cells. I have 
made careful examinations of longitudinal sections of very 
many growing apices, and find no evidence in support of his 
statement or figure. The ligule appears to me to arise 
invariably from two rows of cells (Fig. 7), which can easily be 
