PLANT ORGANS AND ORGANISMS 
135 
leaves remain dorsiventral, 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 numer- 
ous; 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 abundant, small, 
with narrow slit, and depressed below the level of the epidermis. 
There are live 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 
the Epidermal Daughter-cell. The latter, upon maturing, becomes a 
normal epidermal cell. A partition is laid down lengthwise through 
the Stoma Mother-cell dividing it into two stomatal daughter-cells. 
The wall laid down lengthwise splits and thus forms the orifice of the 
stoma; the cells on either side of the orifice are called Guard Cells. 
These, while at first flat and inoperative, soon become bulged and 
crescent-shaped. This mode of development is seen in Squill, 
Hyacinth, Daffodil, Sambucus, Silene, etc. 
Second Type. — After the cutting off of the stomal mother-cell there 
are cut off on either side portions of neighboring epidermal cells which 
form subsidiary cells to the stoma. This condition is seen in Gram- 
inacece, Cyperacece, Juncacece, in various species of Aloe, Musa and 
Proteacece. 
Third Type .- — Instead of two parallel subsidiary cells, four are cut 
off, as in Heliconia, in species of Tradescanlia, Araucaria, or four to 
five, as in Ficus elastica, or four to five or more, as in the Coniferce 
and Cycads. 
Fourth Type.- — Instead of only four subsidiary cells, each of these 
again subdivides by parallel walls, more rarely by radial walls, into 
eight radiating subsidiary cells, as in Maranta bicolor, Pothos argyraa, 
some of Proteacece, etc. 
Fifth Type . — The “stomal mother-cell” divides once or several 
times before becoming the true mother-cell of the stoma. As a 
result of the divisions there are also formed one or more subsidiary 
