H. M. Leake 229 



dominance, which formed so striking a characteristic of the earlier 

 experiments on these lines, holds no position of fundamental importance 

 in Mendel's own statement of his law. In the present instance there is 

 a complete absence of dominance and the direct offspring of a cross are 

 as markedly distinct from one, as they are from the other, parent. 

 It is possible, however, to discern more than this. The two factors 

 appear capable of blending in any proportion, and there thus appear 

 a continuous series of forms showing all stages from the typical broad 

 lobed individual, with a leaf factor less than 2, to the typical narrow 

 lobed individual with the leaf factor greater than 3. Owing, however, 

 to some influence, of which, as yet, nothing is understood, these various 

 degrees of blending do not occur with equal frequency. This is greatest 

 at the point represented by a blending of equal proportions of the two 

 factors and becomes less and less as this proportion becomes unequal, 

 but increases again when the proportion of one or other of the factors 

 is reduced to a negligible quantity or is entirely absent. 



This capacity of blending in unequal proportions is further shown 

 by a comparison between the value of the leaf factor of the F„ parent 

 with the mean value of that of the F^ offspring. This comparison is 

 given in the three last columns of Table XIV. The difference between 

 these two values for the whole series is 0'07, a figure well within the 

 limit of experimental error, which is, however, in a few individual cases 

 exceeded. It may be generally stated, therefore, that the value of the 

 parental leaf factor is the mean of the values for the offspring. Con- 

 sequently, when unequal blending occurs in any plant, the number of 

 offspring falling within the group whose leaf factor enters in greatest 

 proportion into the blending will exceed the number of offspring which 

 fall within the other group. In other words the ratio of the offspring 

 having a leaf factor less than 2 to offspring having a leaf factor greater 

 than 3 will increase as the parental leaf factor diminishes from the 

 mean value of 2'6 and will conversely diminish as the parental leaf 

 factor increases from this mean. That this is the case the detail 

 columns of Table XIV clearly show. 



It is now necessary to glance for a moment at the lower limit of the 

 " narrow " lobed group. It has been stated that this limit is 3'0, a 

 figure which has, with one exception, been adopted in Table XL 

 Reference to Table XIV, however, will show that the lower limit for 

 the pure forms with narrow lobed leaves is 3"2 — a figure which exceeds 

 the vahie of the corresponding parental leaf factor. In this connection 

 it is noteworthy that a value of 35 is throughout obtained for the 



16—2 



