1923] 



Bau: Morphological Characters in Crepis Capillaris 



2S23 



INHERITANCE OF THE NUMBER OF LOBES 



The problem of the number of lobes on the leaves resolves itself 

 into four distinct subheads. The first of these involves the question 

 whether the leaf shall be considered lobed at all. There are families 

 in which the lobing, if present, is so shallow that the leaves would be 

 described as entire or merely dentate. This type is designated as 



TABLE 2 

 Showing the Eesults of Crossing fob Inheritance of Leaf Length 



Applying Castle's formula 



n 



(29.7 - 17.9)2 139.24 



8(5.282 - 2.332) 179.2 



Factors responsible for length = 1 factor. 



This result is very improbable, but the results can be interpreted on a modified 

 dihybrid ratio of 9:6:1 where the two single homozygous genotypes give identical 

 effects. On this ratio and from a study of the data, the result may be stated thus: 



A B = 9, leaf length from 6 — 18 cm. 



A b = 3, leaf length from 19 — 25 cm. 



a B = 3, leaf length from 19 — 25 cm. 



a b =1, leaf length from 26 — 34 cm. 



Where factors A and B stand for two independent factors in the absence of both 

 of which the double recessive a b is obtained: 



Observed numbers: 491 : 158 : 27 

 Calculated numbers: 378 : 252 : 42. 



simplex in the accompanying account. There is another type where 

 the lobes are distinct and simple and look like the steps on a ladder. 

 This is designated as the scalaris type. A third type has a complex 

 type of lobes where the scalaris type of lobing is surmounted by 

 smaller secondary lobules or wings. The second subhead refers to 

 the incision or depth of lobing. In the families studied the lobing 

 extended halfway from the margin to the mid-rib or completely to 

 the mid-rib. The third subhead concerns number of lobes on the leaf 

 and the fourth refers to the character which is shown when the second- 

 ary lobules instead of remaining attached to the main lobes are 



