II] 



Structural Characters: Plants 



21 



Datura. 



5. Prickliness and smoothness of fruits. 

 (R.E.C. 19, 20.) Ranuncuhis arvensis (20). 



The case of Datura is interesting from the fact that it sometimes has 

 mosaic fruits, one quarter or one half being prickly and the rest smooth. 

 This is perhaps to be regarded as indicative of segregation occurring 

 among zygotic cells (see Chap. xv.). 



Ranunculus arvensis has three types, spiny, tuberculated, and smooth. 

 The first is a simple dominant. Tuberculated x smooth gave F l partially 

 spiny (2 1, p. 55). 



6. Absence of glands (Matthiola incana] on leaves was 

 dominant to presence of glands (M. sinuatd] (R.E.C. 20, 

 p. 40). 



Fig. 5. Cross between a normally awned Barley and a variety with 

 " hooded " awns. P, P, the parents. F l shows partial dominance of 

 hoods. The increase in length of ear is noticeable. The case also 

 illustrates the result of crossing a 2-row type with a 6-row type, 

 showing dominance of the former. (From Professor Biffen's specimens. ) 



