22 
BULLETIN 1038, U. S. DEPARTMENT OF AGRICULTURE. 
Table II. — Variation in the thickness of normal and rosetted pecan leaves, using 
the thickest part of each leaf as the standard of comparison. 
Measurements of thickness. 
Description of material. 
Average. 
Extremes. 
Variation 
average. 
NORMAL LEAVES. 
Frotscher variety, Thomasville, Ga.: 
North side of tree 
Microns. 
162 
147 
168 
158 
167 
152 
158 
118 
113 
139 
151 
198 
140 
Microns. 
131-187 
122-173 
154-187 
108-206 
80-210 
70-215 
72-229 
103-141 
70-173 
75-234 
94-187 
140-281 
78-195 
Per cent. 
18 
South side of tree 
18 
18 
ROSETTED LEAVES. 
Frotscher variety, Thomasville, Ga.: 
Mottled leaves, about half size- 
North side 
38 
South side 
37 
Much-aborted leaves, south side — 
26 
Mottled 
42 
Linear leaves, south side — 
26 
Mottled 
50 
55 
Variety not stated, Cairo, Ga.: 
50 
Van Deman variety: 
45 
47 
The average thickness of linear leaves was always less than that 
of healthy or of other types of rosetted leaves. That this difference 
is not normally related to leaf size was shown by measurements 
comparing the thickness of the large juvenile leaves of normal young 
seedlings with that of the first type leaves above and that of large 
tip leaflets with small basal leaflets on single juvenile leaves. (Table 
III.) In the case of large juvenile leaves as compared with type 
leaves above there was a 67 per cent variation in the area of the 
laminse, but only a 7 per cent variation in thickness. In the vascular 
portion of the large side veins, however, a 72 per cent variation in 
the area of the cross section was correlated with this increase in leaf 
size. (Table IV.) 
Table III. — Leaf thickness and vein diameter as related to size in normal 
young pecan seedlings. 
Description of material. 
Large juvenile leaves 
First type leaves above 
Large Juvenile tip leaflets 
Small juvenile basal leaflets on same leaves 
Thickness (microns). 
Leaf 
average. 
103 
96 
112 
101 
Leaf ex- 
tremes. 
94 to 117 
89 to 103 
98 to 126 
98 to 112 
Large 
veins. 
515 
388 
538 
243 
Leaf variation (per 
cent). 
Thick- 
ness. 
Area. 
