ix] Spurious A ileloinorphism 153 



plants, the sterile to the fertile were 3 to I without com- 

 plication. 



Statistical examination of these families on a large scale 

 has shown that among the plants with coloured flowers 

 the ratio of fertile with dark axil : fertile with light axil : 

 sterile with dark axil : sterile with light axil, approaches 

 closely to that which would be produced if the series of 

 gametes bearing these four respective combinations were 



15 . i : i : 15. 



The actual numbers observed were 



Dark axil Light axil 



Fertile Sterile Fertile Sterile 



627 27 17 214 



Expectation 637 27 27 194 



Repulsion or Spurious Allelomorphism. 



A third example of partial gametic coupling relates again 

 primarily to the blue factor (B) and the pollen-shapes, 

 but in order to make clear the circumstances in which it 

 occurs, another set of phenomena must first be described. 



In the old types of Sweet Pea the standard is erect and 

 has a small notch in the middle of its upper border. This 

 is the natural shape of the wild flower. Of the modern 

 types many are what is called " hooded." The standard in 

 hooded forms turns forward and downward in various de- 

 grees, the amount varying with the type and also to some 

 extent with the weather and the condition of the flower. 

 The hooded standard differs also from the erect one in 

 having little or no trace of the central notch. This differ- 

 ence causes the buds of the two types to be recognizably 

 distinct before the flower opens, for in the hooded type the 

 point of the folded standard projects sharply forward in 

 front of the wings, while in the erect type this tip is rounded 

 off by reason of the notch. (Plate V.) 



The hooded standard also is sometimes distinguished by 

 the existence of a sinus of variable size on each side of the 

 standard, which thus has lateral lobes more or less well 

 developed. These differences obviously point to a different 

 distribution of the strains produced by the growth in the 

 two types. The lateral sinus is not represented in the 

 hooded flowers shown in Plate V. 



