436 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8, 
light were thicker and contained a larger amount of chlorophyll, so that 
fewer veins were visible in a unit area. Schuster (8) records a similar con- 
dition in the leaves of Ampelopsis Veitchii. 
Inasmuch as Benedict found a direct correlation between age differences 
and vein-islet areas in leaves from various perennial plants, some of these 
plants were studied by clearing and staining. The leaves of Fagus caro- 
liniana were taken from plants growing in close proximity to each other 
yet having large differences in trunk diameters. A summary of the data 
from this study is presented in tables. 2 and 3. Although Benedict did not 
study the leaves of the beech, he intimates that the leaves of all the woody 
perennial plants show senescence by the constantly increasing amount of 
vascular tissue in their leaves as they increase in age. The data in tables 
2 and 3 do not show distinctive differences. 
Table 2. Relative Size of Vein-islets of Leaves of Fagus caroliniana Fernald and Rehder, 
from Trees of Different Ages 
Trunk Diameter 5.4 cm. 
Trunk Diameter 22 cm. 
Number of Leaf 
No. Vein-islets 
Area 
No. Vein-islets 
Area 
in Unit Area 
Vein-islets 
in Unit Area 
Vein-islets 
(4 sq, mm.) 
(sq. mm.) 
(4 sq. mm.) 
(sq. mm.) 
I 
63 
.0635 
69 
.0580 
2 
62 
.0645 
64 
.0625 
3 
66 
.0606 
60 
.0666 
4 
63 
.0635 
61 
.0655 
5 
64 
.0625 
65 
.0615 
6 
63 
.0635 
62 
.0645 
7 ■ 
61 
•0655 
62 
.0655 
8 
63 
.0635 
63 
.0635 
9 
60 
.0666 
10 
64 
.0625 
Average 
62.9 
.0637 
63.2 
.0635 
Table 3. Comparison of Size of Vein-islets in Relatio7i to Age of Tree in Fagus caroliniana 
Diameter of Trunk (cm.) 
6.2 
7.5 
18 
20 
.0678 
.0640 
.0641 
.0625 
In leaves from specimens of Castanea dentata having a trunk-diameter 
difference of 49.5 cm., Benedict records a difference in vein-islet area of 
0.3 square millimeter. In table 4 a summary of the findings in cleared 
and stained leaves is shown. Here there is but the very slightest difference 
shown in the area of the vein-islets. The variation found in individual 
leaves from the same tree shows as great differences. 
Table 4. Relation of Size of Vein-islets to Age in Castanea dentata Borkh. 
Diameter of Trunk (cm.) 
5-2 
3-7 
50.4 
38 
Average Area of Vein-islets of 15 Leaves (sq. mm.) 
.0897 
.0697 
.0876 
.0677 
