XIII 



CERTAIN COMPLICATIONS 



155 



was raised from the F^ plants. All the F^ plants 

 from the pollen of the double-throwing single behaved 

 like double-throwing singles, but of the F^ plants 

 from the ovules of the double -throwers some behaved 

 as double-throwers and some as pure singles. We 

 are led to infer, therefore, that the ovules and pollen 

 grains of the double-throwers, though both produced 

 by the same plant, differ in their relation to the 

 factor (or factors) for doubleness. Doubleness is 



Single 



Single 



1 



Double 



Ovule of 



Pollen of y o^ ^ . p. ii_ X ^"""'^ ° , 



pure single ^ ^^^^^ ^ °"^" ^ Pure single 



Single 



I 



Single 



Single 



Single 



I 1 



Single Double 



Single Double 



I 1 



Single Single Double 



Single Double 



apparently carried by all the pollen grains of such 

 plants, but only by some of the ovules. Though 

 the nature of doubleness in stocks is not yet clearly 

 understood, the facts discovered by IMiss Saunders 

 suggest strongly that the ovules and pollen grains 

 of the same plant may differ in their transmitting 

 properties, probably owing to some process of 

 segregation in the growing plant which leads to 

 an unequal distribution of some or other factors to 

 the cells which give rise to the ovules as compared 

 with those from which the pollen grains eventually 



