HOMOTYPOSIS IN THE VEGETABLE KINGDOM. 
303 
(9.) C. Beech (Fagus sylvatica). Number of Veins on the Leaf —I have here only 
one series of 26 leaves from each of 100 trees. These were gathered and counted by 
Mrs. Karl Pearson and myself in the neighbourhood of Great Hampden. The 
trees were in part fine isolated specimens growing on the commons, but as there were 
not sufficient of these we were compelled to gather from the somewhat smaller trees 
abounding in the beechwoods of this part of Buckinghamshire. The leaves were 
gathered about 4 to 5 feet from the ground on the outside of the tree.* The 
tabulation of the results and the calculation of the constants are again the work of 
Dr. Lee. 
Hampden Beech Leaves. 
Number. 
Mean number 
of veins. 
S.D. of 
veins. 
Correlation 
of pairs. 
Trees. 
Leaves. 
Pairs. 
100 
2600 
65,000 
16-1062 
± -0230 
1-7351 
± -0162 
-5699 
[± -0087] 
Distribution of Number of Veins. 
Number of veins... 
10 
11 
12 
13 
14 
15 
16 
1 
17 i 18 19 
1 
. 
20 
. 
21 
1 
0 0 ! 
1 
Total. 
Frequency . 
1 
1 
7 
34 
110 
318 
479 
595 
516 j 307 181 
36 
15 
1 1 
1 
2600 
Individual and Bacial Variation. 
S.D. 
S.D. of array. 
Coefficient of variation. 
Percentage variability. 
1-7351 
1-4258 
10-77 
82-17 
Accordingly, we see that the modal value of the beech leaf veins is 16, which is 
very near the mean, 16T1. The standard deviation about 1‘7, and the degree of 
resemblance among its leaves ’57 Measured by its coefficient of variation, it is the 
least variable of the trees so far dealt with, and the leaves of the same tree more 
closely resemble each other. Notwithstanding its relatively small variability, the 
individual on an average exhibits about 82 per cent, of the racial variability. 
The table of reduced data is given below. 
* I did not observe among the leaves gathered anything of the differentiation indicated by Professor 
Macleod between “licht- en schadernbladen.” The material, so far as this character (number of veins) 
goes, seemed singularly homo eneous and of small variability. 
