HOMOTYPOSIS IN THE VEGETABLE KINGDOM. 
349 
Of course the groupings here are large, but the distribution notwithstanding the 
mixture of material seems more regular than in some of our other series. 
The following scheme gives the constants in the usual manner : 
Leaf Index of Wild Ivy. 
Number of 
Mean 
index. 
S. D. 
Coefficient 
of 
variation. 
S. D. of 
array. 
Percentage 
variation. 
Correlation. 
Plants. 
Leaves. 
Pairs. 
100 
2500 
60,000 
•8473 
± -0020 
•1506 
± -0014 
17-7735 
•1449 
96-21 
•2726 
[± -0125] 
It will be observed that the correlation is lower than we might have expected, 
although the mean of the index correlations for mushroom gills and ivy leaves, he., 
^ (•5490 + '2726) ='4108, is almost identical with the value ’4 given for brothers by 
the law of ancestral heredity. The low value of the correlation gives of course a 
high value to the percentage variation, the variation of the individual plant being 
within 4 per cent, of the racial variation. The variability of the ivy leaf, as judged 
by this character, has not the intensity which is popularly associated with it; it is 
sensibly less than that of the mushroom gill, and about equal to that of the tunics 
of the onion. 
I now pass to the absolute measurements of the leaf. 
Dr. Warren" being much pressed with other work, kindly placed all Ills measure¬ 
ments at my disposal, and I proceeded to draw up the same four tallies as in the 
case of the mushroom gills. The work here was, however, much more laborious as I 
had to deal with 25 leaves instead of 10 gills, and this involved 300 pairs for each 
plant, instead of only 45 ! In the course of a fortnight’s work I had completed the 
length-breadth organic correlation, the length-length homotypic correlation, and about 
a third of the length-breadth homotypic correlation. At this point Dr. Lee took the 
work off my hands and finished the last table and the breadth-breadth homotypic 
correlation. So that the residts are again the product of co-operation.'^' I give 
below the data arranged as in the case of the mushroom gills. The dimensions are 
given in eighths of inches. 
* AVe lia\e now .systematiserl the working of these long tables, involving 10,000 to 60,000 entries 
providing appropriate checks for accuracy up to each stage of construction. It seems unnecessary to 
describe these here, but we .shall be glad to put our experience at the service of any one working at 
similar problems. At the same time the collection, measurement and formation of a table for the cross 
homotypic correlation of two characters in 25 undifferentiated like organs of 100 individuals will cost a 
sivfjJe worker at least three weeks to a month’s fairly continuous labour. 
