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periphery leaves. Most of this increase was due to the paHsade as it 
more than doubled in thickness. In the center leaves the palisade 
made up 33 percent; the sponge, 45 percent; the upper epidermis, 12 
percent; the lower epidermis, 10 percent the total thickness. In the 
south periphery leaves the palisade made up 57 percent; the sponge, 
24 percent; the upper epidermis, 11 percent; the lower epidermis, 
8 percent of the total thickness. The south periphery leaves had two 
layers of compact palisade, the center leaves one layer. The amount 
of evaporation at the center was 67 percent that at the south periphery, 
and the light was 0.082. 
Ulmus americana. — The thickness of the center leaves of an isolated 
Ulmus americana was 64 percent the thickness of the south periphery 
leaves. The palisade in the former was 45 percent the thickness of 
that in the latter. In the center leaves the palisade made up 35 per- 
cent of the total thickness, the sponge 38 percent, the upper epidermis 
16 percent, the lower epidermis 11 percent. In the south periphery 
leaves the palisade made made up 50 percent of the total thickness, 
the sponge 26 percent, the upper epidermis 15 percent, the lower 
epidermis 9 percent. 
The south periphery leaves were more compact in structure, the 
cells were narrower and longer, the upper epidermis more regular, and 
two layers of palisade were developed as compared with one in the 
center leaves. The weight of the green center leaves was 71 percent 
that of the south periphery leaves; the water-free leaves, 55 percent. 
The water content of the center leaves was 66 percent, of the south 
periphery leaves 56 percent. 
The amount of evaporation at the center was 69 percent; the wind 
57 percent the amounts at the periphery The light intensity at the 
center was 0.084. 
Fraxinus pennsylvanica. — The thickness of the center leaves of an 
isolated Fraxinus pennsylvanica was 63 percent that of the south 
periphery leaves. The palisade in the former was 38 percent the 
thickness in the latter. In the center leaves the palisade made up 35 
percent the total thickness, the sponge 50 percent, the upper epidermis 
8 percent, the lower epidermis 7 percent. In the south periphery 
leaves the palisade made up 58 percent the total thickness, the sponge 
30 percent, the upper epidermis 6.4 percent, the lower epidermis 5.6 
percent. 
The south periphery leaves were frequently entirely palisaded; 
