i 74 
PHARMACEUTICAL BOTANY 
The epidermal cells which abut on the stomatal apparatus are 
called neighboring cells or subsidiary cells. These in many cases, as 
in species of Helleborus, Sambuscus, Hyacinthus , Pceonia , Ferns, etc., 
are very similar to the other epidermal cells, but in a large number of 
plants they differ in size, arrangement and shape from the other 
cells of the epidermis which do not abut upon the stomatal apparatus. 
In Senna they are two in number one larger than the other and 
arranged parallel to the guard cells of the stoma; in Coca a similar 
arrangement occurs but the cells are more even in size, nevertheless 
they lack the characteristic papillae found on the other epidermal 
cells; in Pilocarpus they are usually four in number but quite narrow 
and more or less crescent-sl aped; in TJva Ur si their number is usu¬ 
ally seven to eight and their arrangement radial around the stomata 
apparatus. 
On all dorsoventral leaves, the stomata arise more abundantly on 
the lower epidermis, less abundantly on .the upper. Exceptions to 
this rule are due to the peculiar readaptation of the leaf to its sur¬ 
roundings. Thus, in the reversed types of leaves (twisted in a half 
circle) the stomata, formerly on the lower surface, have migrated to 
the upper surface which now has become the physiological lower 
surface. 
In Umbrophytic (shade) plants the stomata are either wholly on 
the lower surface or partly so with a number on the upper surface. 
Where the plants are Mesophytic and exposed to dense sunlight and 
leaves remain dorsoventral, the stomata are on the lower surface; 
these stomata are large, if the surroundings are damp. If such 
plants live in dry soil and dry air, the stomata are of small size and 
numerous; if they dwell in dry soil in hot surroundings and dense 
light they are very small and frequently sunk. If the plants are 
Xerophytic and the leaves dorsoventral, the stomata are quite abun¬ 
dant, small, with narrow slit, and depressed below the level of the 
epidermis. 
There are five types of stomatal development, viz.: 
First Type. —Each primitive epidermal cell (or the majority, or 
only certain ones of the epidermis) at the close of the dermatogen 
stage, gradually lengthens and then cuts off a smaller from a larger 
cell. The smaller one is equilateral, has a very large nucleus, and is 
termed the Stoma Mother-cell ; the larger, quadrangular, and called 
