1881.] Tradescantia and Indian Corn. 763 
ducing a cell whose upper surface is rhomboidal (Plate 1, 
Fig. 1). 
This cell soon becomes nearly square, and at this time, lying 
between four nearly equal hexagons, it is a difficult matter to see 
from which it was produced (Fig. 11), The cell lengthens so that 
in a short time it is longer than broad; and the ends are much 
curved, while the sides are nearly straight. The stoma increases 
very little in depth from the first, the subsequent growth being 
nearly all lateral. Soon after the stoma begins to take this oblong 
shape, two cells, of nearly equal size, and somewhat smaller than 
the stoma-cell, are cut out from the two epidermal cells at the 
sides of the stoma (Figs. 1v and v), and a little later, in the same 
way, two similar cells are formed at the ends (Figs. vi and vit). 
Near the time of the formation of these latter cells, the mother- 
cell of the stoma shows a tendency to divide, the cell approaching 
in the meantime nearer and nearer the oval of the perfect stoma. 
A vertical septum is formed, dividing the mother-cell into two, 
and as growth progresses these separate in the middle, forming a 
pore leading to the space beneath (Figs. 1x, x and x1). The con- 
tents of the stoma are, from the first, denser than those of the 
epidermal cells, but chlorophyll does not appear until the stoma 
has attained some size. As it increases in size, the chlorophyll 
becomes more evident, and shows a tendency to collect in masses, 
until in the perfect stoma very distinct chlorophyll bodies are 
present (Figs. xxiv), The accessory cells grow ,in about the 
Same ratio as the stoma, so that they bear nearly the same pro- 
portion to the completed stoma that they did to the stoma when 
they were first formed. The air-cavity beneath the stoma is 
small at first, extending only beneath the stoma proper (Figs. 
Xvil and xvii), but it increases, extending under the accessory 
Cells, until finally it occupies nearly the whole space beneath 
them (Figs. xv, xvi). These cells, as well as the stoma proper, 
increase little in depth after they are first formed. Occasionally 
the accessory cells are more in number, five or six, but this is 
rare, and when it does happen, they are crowded so as to occupy 
little more space than the normal number. 
The first thing that strikes one on examining the epidermis of 
Indian corn, is the peculiar form of the stomata. The guard- 
cells, apparently, instead of being crescent-shaped, are nearly 
triangular, and do not meet at the ends, as would be expected. 
