HARRIS AND AVERY: MORPHOLOGICAL VARIATIONS 117 
as compared with 9.77 per cent. with five and six leaflets in the 
normal controls. 
Taking the average number of leaflets per plant as a basis of 
comparison between the abnormal plants and their controls we 
find the results in TABLE IX. 
TABLE IX 
MEAN NUMBER OF LEAFLETS IN SEEDLINGS OF VARIOUS TYPES 
a Mea 
Class of abnormality — er of number of Difference 
abnormals | controls 
| 
| 
ee ee a aT oa coe ees mao Vcc es 3-170 3-133 | +0.037 
Ne ie ea sar SAE) es 6 woe IE Awe ba a 3.228 3-191 +0.037 
Three dae ais two primordial leaves............. 3-847 | 3.131 | +0.716 
Th tyled three pri dial leaves........... 3-900, 3.204 | +0.606 
Note (a) that for each type of normality the average number 
of leaflets is greater in the abnormal individuals than in the nor- 
mal, and (0) that the difference between the abnormal class and its 
control is far greater in the case of the plants with three cotyledons 
than in those in which the abnormality in the cotyledonary whorl 
consists merely in the separation of the two cotyledons. 
Thus the results for number of leaflets substantiates the con- 
clusion based upon number of leaves. 
Evidently, however, the number of leaflets is to a great extent 
determined by the number of leaves. The problem now arises: 
Are there differences in the average number of leaflets per leaf in 
the abnormal and normal individuals? : 
Means and their differences have been diternined, but are 
so slight that conclusions must be deferred until further series of 
data are available. 
Just one other method of dealing with the problem of the cor- 
relation in structural variation may now be considered. 
Number of leaflets is, in the materials dealt with, practically 
an integral variate. In examining a large series of plants those 
with partial division of a leaflet, representing transition stages 
between a leaf with » and one with m + 1 leaflets are sometimes 
found. Such cases are, however, relatively rare. The lobing of 
the leaflet has therefore been disregarded in the foregoing treat- 
