Copeland ' — The Mechanism of Stomata, 357 
leaf of Azalia nudiflora , after exposure to direct sunlight, 
submerged : — 
Open. 
Closed. 
Length . 
25 
35 
Width of stoma . 
19 
14 
Width of guard-cell 
8 
' 7 
Width of pore 
3 
0 
Fig. 53 shows the structure of a stoma of about the same 
age. 
Fig, 52 is of a still younger one, the rift not yet open, but 
the thin areas already visible. 
Cyclamen , sp. (cultivated). Helleborus type. 
Convolvulus sepium , L. Like Ipomoea hederacea (Figs. 
54> 55)- The stomata on the stems of both of these are 
nearer the Amaryllis type. 
Phlox divaricata , L. Helleborus type. The reinforcement 
of the outer part of the end walls is shown by Fig. 56. 
Gentiana Andrew sii, Griseb. Helleborus ox Achillea type; 
not very uniform, but always greatly thickened ; thickenings 
at ends variable ; most commonly as in Fig. 57. 
Obolaria Virginica ) L. Many abortive and angular : those 
which develop, somewhat like Anthoceros , with internal ventral 
corner thicker. 
Chelone glabra , L. Between Helleborus type and the 
stomata on the cotyledon of Eucalyptus. 
Physostegia Virginiana ) Benth. Achillea type. In the 
stomata of the Labiatae , with a subsidiary cell around each 
end of the stoma, the wall between these, striking the dorsal 
wall of the guard-cell about its middle, is thin and curved, 
usually about 90° : in Mentha viridis the curve is double, 90° 
each way. This curve probably decreases its resistance to the 
movement of the stoma. 
Mentha viridis , L. Helleborus type. 
Salvia lyrata> L. Achillea type. 
Lamium amplexicaule , L. Achillea type. 
Nepeta Glechoma , Benth. Achillea type. 
