THE LEAF 253 
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 the 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 numerous; if they dwell in dry soil in hot sur- 
roundings and dense light they are very small and frequently 
sunken. If the plants are Xerophytic and the leaves dorsiven- 
tral, the stomata are quite abundant, small, with narrow slit, 
and depressed below the level of the epidermis. 
There are five types of stomatal development, viz.: 
First Typr.—Each primitive epidermal cell (or the majority, 
or only certain ones of the epidermis) at the close of the dermato- 
gen 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, quad- 
rangular, 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 length- 
wise 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 Sguzll, Hyacinth, 
Daffodil, Sambucus, Silene, etc. 
SEconp Type.—After the cutting off of the stomal mother- 
cell, there are ¢ut off, on either side, portions of neighboring 
epidermal cells which form subsidiary cells to the stoma. This 
condition is seen in Gramineae, Cyperacea, Juncacee, in various 
species of Aloe, Musa and Proteacea. 
Turp Type.—Instead of two parallel subsidiary cells, four 
are cut off, as in Heliconia, in species of Tradescantia, Araucaria, or 
four to five, as in Ficus elastica, or four to five or more, as in the 
Conifere and Cycads. 
Fourtu Type.—Instead of only four subsidiary cells, each of 
these again subdivides by parallel walls, more rarely by radial 
