X 



SEX 115 



is of interest The peculiar cretin form, described 

 on p. 79, never sets seed though the pods and 

 seeds may often begin to swell ; it is always sterile 

 on the female side though the pollen may be 

 perfectly good. When a normal sweet-pea with 

 aborted pollen, practically a female, is fertilised by 

 pollen from a cretin, practically a male, plants with 

 normal hermaphrodite flowers are produced. From 

 these, on self-fertilisation, the four expected classes 

 arise as shown in Fig. 38. Among them is the 

 cretin with sterile pollen, a plant incapable of repro- 

 duction either on the 



mal^ nr f/^ma1p cirl^ Normal with \ /Cretin with 



male or temale side. sterile pollen|X (^fertile pollen 



The proportions in 



which the four classes ^f°!^,*^ 



fertile 



appear is peculiar, and I 



will be discussed in | 1 ' — i 1 



detail in the next Normal Normal Cretin Cretm 



fertile sterile fertile sterile 



chapter, when we come 33 15 15 i 



to deal with the coup- P,^, g, 



ling and repulsion of 



genetic factors. From the present standpoint it is of 

 interest to note that the majority of the normal fertiles 

 in F behave as the F normal fertile, giving all four 

 classes in the same proportions. Of the normal 

 steriles, again, the majority are homozygous for the 

 normal factor, while the majority of the cretins are 

 homozygous for the factor which leads to the produc- 

 tion of fertile pollen. Owing to the peculiar relation 

 between the factors, which will be explained shortly, 

 there is a tendency for the hermaphrodite, produced 

 by the union between a male and a female, to give 

 only males, females, and hermaphrodites. Were the 



